docs/master: discussion.roff annotate

docs/master

annotate discussion.roff @ 197:05a243dffaca

Added refs to the Preface; splitted the bib.

author	markus schnalke <meillo@marmaro.de>
date	Thu, 12 Jul 2012 00:39:41 +0200
parents	5360f5fdb118
children	5cd9bacdfcd3

rev	line source
meillo@58	1 .H0 "Discussion
meillo@0	2 .P
meillo@169	3 This main chapter discusses the practical work accomplished in the
meillo@169	4 mmh project.
meillo@169	5 It is structured along the goals set for the project.
meillo@169	6 The concrete work undertaken
meillo@58	7 is described in the examples of how the general goals were achieved.
meillo@87	8 The discussion compares the current version of mmh with the state of
meillo@171	9 nmh just before the mmh project started, i.e. fall 2011.
meillo@87	10 Current changes of nmh will be mentioned only as side notes.
meillo@87	11 .\" XXX where do I discuss the parallel development of nmh?
meillo@187	12 .P
meillo@187	13 For the reader's convenience, the structure of modern email systems
meillo@187	14 is depicted in the figure.
meillo@187	15 It illustrates the path a message takes from sender to recipient.
meillo@187	16 .sp
meillo@187	17 .KS
meillo@187	18 .in 2c
meillo@187	19 .so input/mail-agents.pic
meillo@187	20 .KE
meillo@187	21 .sp
meillo@187	22 .LP
meillo@187	23 The ellipses denote mail agents, i.e. different jobs in email processing:
meillo@187	24 .IP "Mail User Agent (MUA)
meillo@187	25 The only program the user interacts directly with.
meillo@187	26 It includes functions to compose new mail, display received mail,
meillo@187	27 and to manage the mail storage.
meillo@187	28 Also called \fImail client\fP.
meillo@187	29 .IP "Mail Submission Agent (MSA)
meillo@187	30 A special kind of Mail Transfer Agent, used to submit mail into the
meillo@187	31 mail transport system.
meillo@187	32 .IP "Mail Transfer Agent (MTA)
meillo@187	33 A node in the mail transport system.
meillo@187	34 Transfers incoming mail to a transport node nearer to the final destination.
meillo@187	35 It may be the final destination itself.
meillo@187	36 .IP "Mail Delivery Agent (MDA)
meillo@187	37 Delivers mail by storing it onto disk, usually according to a set of rules.
meillo@187	38 .IP "Mail Retrieval Agent (MRA)
meillo@187	39 Initiates the transfer of mail from a remote server to the local machine.
meillo@187	40 (The dashed arrow represents the pull request.)
meillo@187	41 .P
meillo@187	42 The dashed boxes represent groups that usually reside on single machines.
meillo@187	43 The box on the lower left represents the sender's local system.
meillo@187	44 The box on the upper left represents the first mail transfer node.
meillo@187	45 The box on the upper right represents the transfer node responsible for the
meillo@187	46 destination address.
meillo@187	47 The box on the lower right represents the recipient's local system.
meillo@187	48 Often, the boxes above the dotted line are servers on the Internet.
meillo@187	49 Many mail clients, including nmh, have all of the components below
meillo@187	50 the dotted line implemented.
meillo@187	51 Not so in mmh, which is an MUA only.
meillo@187	52
meillo@187	53
meillo@187	54
meillo@58	55
meillo@58	56
meillo@58	57
meillo@133	58 .\" --------------------------------------------------------------
meillo@125	59 .H1 "Streamlining
meillo@58	60
meillo@0	61 .P
meillo@169	62 MH once provided anything necessary for email handling.
meillo@169	63 The community around nmh has the similar understanding that nmh should
meillo@169	64 provide a complete email system.
meillo@178	65 In fundamental contrast, mmh shall be an MUA only.
meillo@87	66 I believe that the development of all-in-one mail systems is obsolete.
meillo@173	67 Today, email is too complex to be fully covered by a single project.
meillo@173	68 Such a project will not be able to excel in all aspects.
meillo@159	69 Instead, the aspects of email should be covered by multiple projects,
meillo@87	70 which then can be combined to form a complete system.
meillo@169	71 Excellent implementations for the various aspects of email already exist.
meillo@87	72 Just to name three examples: Postfix is a specialized MTA,
meillo@159	73 .\" XXX homepages verlinken
meillo@87	74 Procmail is a specialized MDA, and Fetchmail is a specialized MRA.
meillo@89	75 I believe that it is best to use such specialized tools instead of
meillo@87	76 providing the same function again as a side-component in the project.
meillo@164	77 .\" XXX mail agent picture here
meillo@58	78 .P
meillo@169	79 Doing something well requires focusing on a small set of specific aspects.
meillo@169	80 Under the assumption that development focussed on a particular area
meillo@169	81 produces better results there, specialized projects will be superior
meillo@87	82 in their field of focus.
meillo@87	83 Hence, all-in-one mail system projects \(en no matter if monolithic
meillo@87	84 or modular \(en will never be the best choice in any of the fields.
meillo@169	85 Even in providing the best consistent all-in-one system, they are likely
meillo@87	86 to be beaten by projects that focus only on integrating existing mail
meillo@169	87 components to create a homogeneous system.
meillo@87	88 .P
meillo@173	89 The limiting resource in the community development of free software
meillo@87	90 is usually man power.
meillo@171	91 .\" XXX FIXME ref!
meillo@87	92 If the development power is spread over a large development area,
meillo@87	93 it becomes even more difficult to compete with the specialists in the
meillo@87	94 various fields.
meillo@87	95 The concrete situation for MH-based mail systems is even tougher,
meillo@169	96 given their small and aged community, concerning both developers and users.
meillo@87	97 .P
meillo@87	98 In consequence, I believe that the available development resources
meillo@100	99 should focus on the point where MH is most unique.
meillo@87	100 This is clearly the user interface \(en the MUA.
meillo@125	101 Peripheral parts should be removed to streamline mmh for the MUA task.
meillo@60	102
meillo@60	103
meillo@100	104 .H2 "Mail Transfer Facilities
meillo@154	105 .Id mail-transfer-facilities
meillo@60	106 .P
meillo@60	107 In contrast to nmh, which also provides mail submission and mail retrieval
meillo@178	108 agents, mmh is an MUA only.
meillo@100	109 This general difference initiated the development of mmh.
meillo@169	110 The removal of the mail transfer facilities was the first work task
meillo@76	111 in the mmh project.
meillo@60	112 .P
meillo@169	113 Focusing on one mail agent role only, is motivated by Eric Allman's
meillo@105	114 experience with Sendmail.
meillo@159	115 He identified the limitation of Sendmail to the MTA task as one reason for
meillo@105	116 its success:
meillo@105	117 .[ [
meillo@105	118 costales sendmail
meillo@105	119 .], p. xviii]
meillo@105	120 .QS
meillo@105	121 Second, I limited myself to the routing function \(en
meillo@110	122 I wouldn't write user agents or delivery back-ends.
meillo@105	123 This was a departure of the dominant through of the time,
meillo@105	124 in which routing logic, local delivery, and often the network code
meillo@105	125 were incorporated directly into the user agents.
meillo@105	126 .QE
meillo@105	127 .P
meillo@187	128 In nmh, the MSA is called \fIMessage Transfer Service\fP (MTS).
meillo@105	129 This facility, implemented by the
meillo@105	130 .Pn post
meillo@105	131 command, established network connections and spoke SMTP to submit
meillo@159	132 messages to be relayed to the outside world.
meillo@169	133 The changes in email demanded changes in this part of nmh as well.
meillo@89	134 Encryption and authentication for network connections
meillo@87	135 needed to be supported, hence TLS and SASL were introduced into nmh.
meillo@87	136 This added complexity to nmh without improving it in its core functions.
meillo@87	137 Also, keeping up with recent developments in the field of
meillo@87	138 mail transfer requires development power and specialists.
meillo@169	139 In mmh, this whole facility was simply cut off.
meillo@76	140 .Ci f6aa95b724fd8c791164abe7ee5468bf5c34f226
meillo@76	141 .Ci fecd5d34f65597a4dfa16aeabea7d74b191532c3
meillo@76	142 .Ci 156d35f6425bea4c1ed3c4c79783dc613379c65b
meillo@87	143 Instead, mmh depends on an external MSA.
meillo@60	144 The only outgoing interface available to mmh is the
meillo@60	145 .Pn sendmail
meillo@87	146 command, which almost any MSA provides.
meillo@87	147 If not, a wrapper program can be written.
meillo@87	148 It must read the message from the standard input, extract the
meillo@87	149 recipient addresses from the message header, and hand the message
meillo@87	150 over to the MSA.
meillo@87	151 For example, a wrapper script for qmail would be:
meillo@87	152 .VS
meillo@87	153 #!/bin/sh
meillo@138	154 exec qmail-inject # ignore command line arguments
meillo@87	155 VE
meillo@87	156 The requirement to parse the recipient addresses out of the message header
meillo@87	157 is likely to be removed in the future.
meillo@169	158 Then mmh would pass the recipient addresses as command line arguments.
meillo@100	159 This appears to be the better interface.
meillo@87	160 .\" XXX implement it
meillo@60	161 .P
meillo@60	162 To retrieve mail, the
meillo@60	163 .Pn inc
meillo@187	164 command acted as an MRA.
meillo@100	165 It established network connections
meillo@76	166 and spoke POP3 to retrieve mail from remote servers.
meillo@76	167 As with mail submission, the network connections required encryption and
meillo@87	168 authentication, thus TLS and SASL were added.
meillo@169	169 Support for message retrieval through IMAP will soon become necessary
meillo@169	170 additions, too, and likewise for any other changes in mail transfer.
meillo@100	171 Not so for mmh because it has dropped the support for retrieving mail
meillo@100	172 from remote locations.
meillo@76	173 .Ci ab7b48411962d26439f92f35ed084d3d6275459c
meillo@76	174 Instead, it depends on an external tool to cover this task.
meillo@169	175 Mmh has two paths for messages to enter mmh's mail storage:
meillo@100	176 (1) Mail can be incorporated with
meillo@60	177 .Pn inc
meillo@87	178 from the system maildrop, or (2) with
meillo@60	179 .Pn rcvstore
meillo@87	180 by reading them, one at a time, from the standard input.
meillo@60	181 .P
meillo@60	182 With the removal of the MSA and MRA, mmh converted from an all-in-one
meillo@178	183 mail system to being an MUA only.
meillo@60	184 Now, of course, mmh depends on third-party software.
meillo@87	185 An external MSA is required to transfer mail to the outside world;
meillo@60	186 an external MRA is required to retrieve mail from remote machines.
meillo@169	187 Excellent implementations of such software exist,
meillo@159	188 which likely are superior than the internal version.
meillo@159	189 Additionally, the best suiting programs can be freely chosen.
meillo@60	190 .P
meillo@60	191 As it had already been possible to use an external MSA or MRA,
meillo@60	192 why not keep the internal version for convenience?
meillo@159	193 .\" XXX ueberleitung
meillo@76	194 The question whether there is sense in having a fall-back pager in all
meillo@76	195 the command line tools, for the cases when
meillo@60	196 .Pn more
meillo@60	197 or
meillo@60	198 .Pn less
meillo@173	199 are not available, appears to be ridiculous.
meillo@100	200 Of course, MSAs and MRAs are more complex than text pagers
meillo@87	201 and not necessarily available but still the concept of orthogonal
meillo@87	202 design holds: ``Write programs that do one thing and do it well.''
meillo@87	203 .[
meillo@87	204 mcilroy unix phil
meillo@87	205 p. 53
meillo@87	206 .]
meillo@87	207 .[
meillo@87	208 mcilroy bstj foreword
meillo@87	209 .]
meillo@87	210 Here, this part of the Unix philosophy was applied not only
meillo@87	211 to the programs but to the project itself.
meillo@87	212 In other words:
meillo@164	213 Develop projects that focus on one thing and do it well.
meillo@169	214 Projects which have grown complex should be split, for the same
meillo@169	215 reasons that programs which have grown complex should be split.
meillo@100	216 If it is conceptionally more elegant to have the MSA and MRA as
meillo@87	217 separate projects then they should be separated.
meillo@169	218 In my opinion, this is the case here.
meillo@87	219 The RFCs propose this separation by clearly distinguishing the different
meillo@87	220 mail handling tasks.
meillo@87	221 .[
meillo@87	222 rfc 821
meillo@87	223 .]
meillo@87	224 The small interfaces between the mail agents support the separation.
meillo@76	225 .P
meillo@169	226 Email once had been small and simple.
meillo@100	227 At that time,
meillo@60	228 .Pn /bin/mail
meillo@169	229 had covered everything there was to email and still was small and simple.
meillo@100	230 Later, the essential complexity of email increased.
meillo@87	231 (Essential complexity is the complexity defined by the problem itself.\0
meillo@87	232 .[[
meillo@87	233 brooks no silver bullet
meillo@87	234 .]])
meillo@171	235 Email systems reacted to this change: they grew.
meillo@100	236 RFCs started to introduce the concept of mail agents to separate the
meillo@100	237 various tasks because they became more extensive and new tasks appeared.
meillo@100	238 As the mail systems grew even more, parts were split off.
meillo@169	239 For instance, a POP server was included in the original MH;
meillo@169	240 it was removed in nmh.
meillo@164	241 Now is the time to go one step further and split off the MSA and MRA, too.
meillo@87	242 Not only does this decrease the code size of the project,
meillo@169	243 more importantly, it unburdens mmh of the whole field of
meillo@87	244 message transfer with all its implications for the project.
meillo@169	245 There is no more need for concern with changes in network transfer.
meillo@169	246 This independence is gained by depending on an external program
meillo@76	247 that covers the field.
meillo@76	248 Today, this is a reasonable exchange.
meillo@60	249 .P
meillo@159	250 .\" XXX ueberleitung ???
meillo@100	251 Functionality can be added in three different ways:
meillo@171	252 .LI 1
meillo@169	253 Implementing the function in the project itself.
meillo@171	254 .LI 2
meillo@87	255 Depending on a library that provides the function.
meillo@171	256 .LI 3
meillo@87	257 Depending on a program that provides the function.
meillo@171	258 .LP
meillo@159	259 .\" XXX Rework sentence
meillo@169	260 While implementing the function in the project itself leads to the
meillo@169	261 largest increase in code size and requires the most maintenance
meillo@169	262 and development work,
meillo@169	263 it increases the project's independence of other software the most.
meillo@169	264 Using libraries or external programs requires less maintenance work
meillo@87	265 but introduces dependencies on external software.
meillo@169	266 Programs have the smallest interfaces and provide the best separation,
meillo@87	267 but possibly limit the information exchange.
meillo@169	268 External libraries are more strongly connected than external programs,
meillo@169	269 thus information can be exchanged in a more flexible manner.
meillo@87	270 Adding code to a project increases maintenance work.
meillo@87	271 .\" XXX ref
meillo@159	272 Implementing complex functions in the project itself adds
meillo@87	273 a lot of code.
meillo@87	274 This should be avoided if possible.
meillo@169	275 Hence, the dependencies only change in their character,
meillo@169	276 not in their existence.
meillo@66	277 In mmh, library dependencies on
meillo@66	278 .Pn libsasl2
meillo@66	279 and
meillo@66	280 .Pn libcrypto /\c
meillo@66	281 .Pn libssl
meillo@159	282 were traded against program dependencies on an MSA and an MRA.
meillo@159	283 This also meant trading build-time dependencies against run-time
meillo@87	284 dependencies.
meillo@169	285 Besides providing stronger separation and greater flexibility,
meillo@169	286 program dependencies also allowed
meillo@66	287 over 6\\|000 lines of code to be removed from mmh.
meillo@66	288 This made mmh's code base about 12\\|% smaller.
meillo@87	289 Reducing the project's code size by such an amount without actually
meillo@87	290 losing functionality is a convincing argument.
meillo@87	291 Actually, as external MSAs and MRAs are likely superior to the
meillo@87	292 project's internal versions, the common user even gains functionality.
meillo@66	293 .P
meillo@169	294 Users of MH should not have problems setting up an external MSA and MRA.
meillo@60	295 Also, the popular MSAs and MRAs have large communities and a lot
meillo@169	296 of available documentation.
meillo@169	297 Choices for MSAs range from full-featured MTAs such as
meillo@159	298 .\" XXX refs
meillo@169	299 .I Postfix ,
meillo@169	300 over mid-size MTAs such as
meillo@60	301 .I masqmail
meillo@60	302 and
meillo@169	303 .I dma ,
meillo@169	304 to small forwarders such as
meillo@60	305 .I ssmtp
meillo@60	306 and
meillo@60	307 .I nullmailer .
meillo@60	308 Choices for MRAs include
meillo@60	309 .I fetchmail ,
meillo@60	310 .I getmail ,
meillo@60	311 .I mpop
meillo@60	312 and
meillo@60	313 .I fdm .
meillo@60	314
meillo@60	315
meillo@100	316 .H2 "Non-MUA Tools
meillo@60	317 .P
meillo@87	318 One goal of mmh is to remove the tools that are not part of the MUA's task.
meillo@181	319 Furthermore, any tools that do not significantly improve the MUA's job
meillo@87	320 should be removed.
meillo@87	321 Loosely related and rarely used tools distract from the lean appearance.
meillo@87	322 They require maintenance work without adding much to the core task.
meillo@125	323 By removing these tools, the project shall become more streamlined
meillo@87	324 and focused.
meillo@169	325 In mmh, the following tools are not available anymore:
meillo@62	326 .BU
meillo@58	327 .Pn conflict
meillo@87	328 was removed
meillo@76	329 .Ci 8b235097cbd11d728c07b966cf131aa7133ce5a9
meillo@87	330 because it is a mail system maintenance tool that is not MUA-related.
meillo@87	331 It even checked
meillo@58	332 .Fn /etc/passwd
meillo@58	333 and
meillo@58	334 .Fn /etc/group
meillo@87	335 for consistency, which is completely unrelated to email.
meillo@87	336 A tool like
meillo@87	337 .Pn conflict
meillo@87	338 is surely useful, but it should not be shipped with mmh.
meillo@76	339 .\" XXX historic reasons?
meillo@62	340 .BU
meillo@58	341 .Pn rcvtty
meillo@87	342 was removed
meillo@87	343 .Ci 14767c94b3827be7c867196467ed7aea5f6f49b0
meillo@89	344 because its use case of writing to the user's terminal
meillo@159	345 on receival of mail is obsolete.
meillo@87	346 If users like to be informed of new mail, the shell's
meillo@58	347 .Ev MAILPATH
meillo@87	348 variable or graphical notifications are technically more appealing.
meillo@169	349 Writing directly to terminals is hardly ever desired today.
meillo@169	350 If, though, one prefers this approach, the standard tool
meillo@58	351 .Pn write
meillo@58	352 can be used in a way similar to:
meillo@82	353 .VS
meillo@58	354 scan -file - \| write `id -un`
meillo@82	355 VE
meillo@62	356 .BU
meillo@58	357 .Pn viamail
meillo@159	358 .\" XXX was macht viamail
meillo@87	359 was removed
meillo@87	360 .Ci eda72d6a7a7c20ff123043fb7f19c509ea01f932
meillo@87	361 when the new attachment system was activated, because
meillo@58	362 .Pn forw
meillo@76	363 could then cover the task itself.
meillo@62	364 The program
meillo@58	365 .Pn sendfiles
meillo@62	366 was rewritten as a shell script wrapper around
meillo@58	367 .Pn forw .
meillo@76	368 .Ci 0e82199cf3c991a173e0ac8aa776efdb3ded61e6
meillo@62	369 .BU
meillo@58	370 .Pn msgchk
meillo@159	371 .\" XXX was macht msgchk
meillo@87	372 was removed
meillo@87	373 .Ci bb9360ead7eb7a3fedcce2eeedfc660014e41dbe ,
meillo@87	374 because it lost its use case when POP support was removed.
meillo@76	375 A call to
meillo@58	376 .Pn msgchk
meillo@87	377 provided hardly more information than:
meillo@82	378 .VS
meillo@58	379 ls -l /var/mail/meillo
meillo@82	380 VE
meillo@100	381 It did distinguish between old and new mail, but
meillo@169	382 these details can be retrieved with
meillo@76	383 .Pn stat (1),
meillo@62	384 too.
meillo@100	385 A small shell script could be written to print the information
meillo@76	386 in a similar way, if truly necessary.
meillo@76	387 As mmh's
meillo@76	388 .Pn inc
meillo@87	389 only incorporates mail from the user's local maildrop,
meillo@62	390 and thus no data transfers over slow networks are involved,
meillo@169	391 there is hardly any need to check for new mail before incorporating it.
meillo@62	392 .BU
meillo@58	393 .Pn msh
meillo@87	394 was removed
meillo@76	395 .Ci 916690191222433a6923a4be54b0d8f6ac01bd02
meillo@87	396 because the tool was in conflict with the philosophy of MH.
meillo@76	397 It provided an interactive shell to access the features of MH,
meillo@173	398 but it was not just a shell tailored to the needs of mail handling.
meillo@169	399 Instead, it was one large program that had several MH tools built in.
meillo@76	400 This conflicts with the major feature of MH of being a tool chest.
meillo@76	401 .Pn msh 's
meillo@159	402 main use case had been accessing Bulletin Boards, which have ceased to
meillo@62	403 be popular.
meillo@62	404 .P
meillo@62	405 Removing
meillo@169	406 .Pn msh
meillo@76	407 together with the truly archaic code relicts
meillo@58	408 .Pn vmh
meillo@58	409 and
meillo@169	410 .Pn wmh
meillo@62	411 saved more than 7\\|000 lines of C code \(en
meillo@66	412 about 15\\|% of the project's original source code amount.
meillo@100	413 Having less code \(en with equal readability, of course \(en
meillo@76	414 for the same functionality is an advantage.
meillo@63	415 Less code means less bugs and less maintenance work.
meillo@76	416 As
meillo@63	417 .Pn rcvtty
meillo@63	418 and
meillo@63	419 .Pn msgchk
meillo@87	420 are assumed to be rarely used and can be implemented in different ways,
meillo@87	421 why should one keep them?
meillo@125	422 Removing them streamlines mmh.
meillo@63	423 .Pn viamail 's
meillo@63	424 use case is now partly obsolete and partly covered by
meillo@63	425 .Pn forw ,
meillo@76	426 hence there's no reason to still maintain it.
meillo@63	427 .Pn conflict
meillo@76	428 is not related to the mail client, and
meillo@63	429 .Pn msh
meillo@63	430 conflicts with the basic concept of MH.
meillo@169	431 These two tools might still be useful, but they should not be part of mmh.
meillo@63	432 .P
meillo@169	433 Finally, there is
meillo@76	434 .Pn slocal .
meillo@76	435 .Pn slocal
meillo@76	436 is an MDA and thus not directly MUA-related.
meillo@100	437 It should be removed from mmh, because including it conflicts with
meillo@178	438 the idea that mmh is an MUA only.
meillo@100	439 .Pn slocal
meillo@100	440 should rather become a separate project.
meillo@87	441 However,
meillo@76	442 .Pn slocal
meillo@76	443 provides rule-based processing of messages, like filing them into
meillo@76	444 different folders, which is otherwise not available in mmh.
meillo@87	445 Although
meillo@76	446 .Pn slocal
meillo@169	447 neither pulls in dependencies, nor does it include a separate
meillo@154	448 technical area (cf. Sec.
meillo@154	449 .Cf mail-transfer-facilities ),
meillo@169	450 it still accounts for about 1\\|000 lines of code that need to be maintained.
meillo@76	451 As
meillo@76	452 .Pn slocal
meillo@76	453 is almost self-standing, it should be split off into a separate project.
meillo@76	454 This would cut the strong connection between the MUA mmh and the MDA
meillo@76	455 .Pn slocal .
meillo@87	456 For anyone not using MH,
meillo@87	457 .Pn slocal
meillo@87	458 would become yet another independent MDA, like
meillo@87	459 .I procmail .
meillo@100	460 Then
meillo@87	461 .Pn slocal
meillo@100	462 could be installed without the complete MH system.
meillo@76	463 Likewise, mmh users could decide to use
meillo@76	464 .I procmail
meillo@87	465 without having a second, unused MDA,
meillo@87	466 .Pn slocal ,
meillo@76	467 installed.
meillo@100	468 That appears to be conceptionally the best solution.
meillo@76	469 Yet,
meillo@76	470 .Pn slocal
meillo@87	471 is not split off.
meillo@100	472 I defer the decision over
meillo@78	473 .Pn slocal
meillo@169	474 out of a need for deeper investigation.
meillo@100	475 In the meanwhile, it remains part of mmh.
meillo@159	476 However, its continued existence is not significant because
meillo@100	477 .Pn slocal
meillo@100	478 is unrelated to the rest of the project.
meillo@0	479
meillo@58	480
meillo@133	481
meillo@134	482 .H2 "Displaying Messages
meillo@155	483 .Id mhshow
meillo@131	484 .P
meillo@133	485 Since the very beginning, already in the first concept paper,
meillo@159	486 .\" XXX ref!!!
meillo@58	487 .Pn show
meillo@62	488 had been MH's message display program.
meillo@58	489 .Pn show
meillo@76	490 mapped message numbers and sequences to files and invoked
meillo@58	491 .Pn mhl
meillo@89	492 to have the files formatted.
meillo@173	493 With MIME, this approach was not sufficient anymore.
meillo@100	494 MIME messages can consist of multiple parts. Some parts are not
meillo@100	495 directly displayable and text content might be encoded in
meillo@58	496 foreign charsets.
meillo@58	497 .Pn show 's
meillo@76	498 understanding of messages and
meillo@58	499 .Pn mhl 's
meillo@173	500 display capabilities could not cope with the task any longer.
meillo@62	501 .P
meillo@88	502 Instead of extending these tools, additional tools were written from
meillo@88	503 scratch and added to the MH tool chest.
meillo@88	504 Doing so is encouraged by the tool chest approach.
meillo@88	505 Modular design is a great advantage for extending a system,
meillo@88	506 as new tools can be added without interfering with existing ones.
meillo@62	507 First, the new MIME features were added in form of the single program
meillo@58	508 .Pn mhn .
meillo@58	509 The command
meillo@82	510 .Cl "mhn -show 42
meillo@58	511 would show the MIME message numbered 42.
meillo@58	512 With the 1.0 release of nmh in February 1999, Richard Coleman finished
meillo@58	513 the split of
meillo@58	514 .Pn mhn
meillo@88	515 into a set of specialized tools, which together covered the
meillo@88	516 multiple aspects of MIME.
meillo@88	517 One of them was
meillo@69	518 .Pn mhshow ,
meillo@88	519 which replaced
meillo@88	520 .Cl "mhn -show" .
meillo@88	521 It was capable of displaying MIME messages appropriately.
meillo@62	522 .P
meillo@88	523 From then on, two message display tools were part of nmh,
meillo@76	524 .Pn show
meillo@76	525 and
meillo@76	526 .Pn mhshow .
meillo@88	527 To ease the life of users,
meillo@69	528 .Pn show
meillo@69	529 was extended to automatically hand the job over to
meillo@69	530 .Pn mhshow
meillo@69	531 if displaying the message would be beyond
meillo@69	532 .Pn show 's
meillo@69	533 abilities.
meillo@88	534 In consequence, the user would simply invoke
meillo@69	535 .Pn show
meillo@69	536 (possibly through
meillo@69	537 .Pn next
meillo@69	538 or
meillo@69	539 .Pn prev )
meillo@69	540 and get the message printed with either
meillo@69	541 .Pn show
meillo@69	542 or
meillo@69	543 .Pn mhshow ,
meillo@69	544 whatever was more appropriate.
meillo@69	545 .P
meillo@69	546 Having two similar tools for essentially the same task is redundant.
meillo@173	547 Usually, users would not distinguish between
meillo@88	548 .Pn show
meillo@88	549 and
meillo@88	550 .Pn mhshow
meillo@88	551 in their daily mail reading.
meillo@88	552 Having two separate display programs was therefore mainly unnecessary
meillo@88	553 from a user's point of view.
meillo@88	554 Besides, the development of both programs needed to be in sync,
meillo@76	555 to ensure that the programs behaved in a similar way,
meillo@76	556 because they were used like a single tool.
meillo@76	557 Different behavior would have surprised the user.
meillo@69	558 .P
meillo@69	559 Today, non-MIME messages are rather seen to be a special case of
meillo@100	560 MIME messages, although it is the other way round.
meillo@69	561 As
meillo@69	562 .Pn mhshow
meillo@159	563 had already been able to display non-MIME messages, it appeared natural
meillo@69	564 to drop
meillo@69	565 .Pn show
meillo@69	566 in favor of using
meillo@69	567 .Pn mhshow
meillo@69	568 exclusively.
meillo@88	569 .Ci 4c1efddfd499300c7e74263e57d8aa137e84c853
meillo@88	570 Removing
meillo@88	571 .Pn show
meillo@88	572 is no loss in function, because functionally
meillo@88	573 .Pn mhshow
meillo@88	574 covers it completely.
meillo@88	575 The old behavior of
meillo@88	576 .Pn show
meillo@88	577 can still be emulated with the simple command line:
meillo@88	578 .VS
meillo@88	579 mhl `mhpath c`
meillo@88	580 VE
meillo@88	581 .P
meillo@76	582 For convenience,
meillo@76	583 .Pn mhshow
meillo@88	584 was renamed to
meillo@88	585 .Pn show
meillo@88	586 after
meillo@88	587 .Pn show
meillo@88	588 was gone.
meillo@88	589 It is clear that such a rename may confuse future developers when
meillo@88	590 trying to understand the history.
meillo@88	591 Nevertheless, I consider the convenience on the user's side,
meillo@88	592 to call
meillo@88	593 .Pn show
meillo@88	594 when they want a message to be displayed, to outweigh the inconvenience
meillo@88	595 on the developer's side when understanding the project history.
meillo@69	596 .P
meillo@88	597 To prepare for the transition,
meillo@69	598 .Pn mhshow
meillo@69	599 was reworked to behave more like
meillo@69	600 .Pn show
meillo@69	601 first.
meillo@154	602 (cf. Sec.
meillo@154	603 .Cf mhshow )
meillo@164	604 .\" XXX code commits?
meillo@88	605 Once the tools behaved more alike, the replacing appeared to be
meillo@88	606 even more natural.
meillo@88	607 Today, mmh's new
meillo@69	608 .Pn show
meillo@159	609 has become the one single message display program once more,
meillo@159	610 with the difference
meillo@88	611 that today it handles MIME messages as well as non-MIME messages.
meillo@88	612 The outcome of the transition is one program less to maintain,
meillo@88	613 no second display program for users to deal with,
meillo@88	614 and less system complexity.
meillo@69	615 .P
meillo@88	616 Still, removing the old
meillo@69	617 .Pn show
meillo@88	618 hurts in one regard: It had been such a simple program.
meillo@159	619 Its lean elegance is missing from the new
meillo@159	620 .Pn show ,
meillo@159	621 .\" XXX
meillo@159	622 however there is no alternative;
meillo@159	623 supporting MIME demands higher essential complexity.
meillo@58	624
meillo@134	625 .ig
meillo@134	626 XXX
meillo@134	627 Consider including text on scan listings here
meillo@58	628
meillo@134	629 Scan listings shall not contain body content. Hence, removed this feature.
meillo@134	630 Scan listings shall operator on message headers and non-message information
meillo@134	631 only. Displaying the beginning of the body complicates everything too much.
meillo@134	632 That's no surprise, because it's something completely different. If you
meillo@134	633 want to examine the body, then use show(1)/mhshow(1).
meillo@134	634 Changed the default scan formats accordingly.
meillo@134	635 .Ci 70b2643e0da8485174480c644ad9785c84f5bff4
meillo@134	636 ..
meillo@131	637
meillo@131	638
meillo@131	639
meillo@133	640
meillo@100	641 .H2 "Configure Options
meillo@58	642 .P
meillo@76	643 Customization is a double-edged sword.
meillo@76	644 It allows better suiting setups, but not for free.
meillo@76	645 There is the cost of code complexity to be able to customize.
meillo@76	646 There is the cost of less tested setups, because there are
meillo@171	647 more possible setups and especially corner cases.
meillo@159	648 Additionally, there is the cost of choice itself.
meillo@76	649 The code complexity directly affects the developers.
meillo@173	650 Less tested code affects both users and developers.
meillo@159	651 The problem of choice affects the users, for once by having to choose,
meillo@159	652 but also by more complex interfaces that require more documentation.
meillo@159	653 Whenever options add few advantages but increase the complexity of the
meillo@159	654 system, they should be considered for removal.
meillo@72	655 I have reduced the number of project-specific configure options from
meillo@72	656 fifteen to three.
meillo@74	657
meillo@76	658 .U3 "Mail Transfer Facilities
meillo@74	659 .P
meillo@85	660 With the removal of the mail transfer facilities five configure
meillo@85	661 options vanished:
meillo@85	662 .P
meillo@85	663 The switches
meillo@85	664 .Sw --with-tls
meillo@85	665 and
meillo@85	666 .Sw --with-cyrus-sasl
meillo@89	667 had activated the support for transfer encryption and authentication.
meillo@159	668 .\" XXX cf
meillo@159	669 .\" XXX gruende kurz wiederholen
meillo@85	670 This is not needed anymore.
meillo@85	671 .Ci fecd5d34f65597a4dfa16aeabea7d74b191532c3
meillo@85	672 .Ci 156d35f6425bea4c1ed3c4c79783dc613379c65b
meillo@85	673 .P
meillo@159	674 .\" XXX cf
meillo@159	675 .\" XXX ``For the same reason ...''
meillo@85	676 The configure switch
meillo@85	677 .Sw --enable-pop
meillo@85	678 activated the message retrieval facility.
meillo@85	679 The code area that would be conditionally compiled in for TLS and SASL
meillo@85	680 support had been small.
meillo@85	681 The conditionally compiled code area for POP support had been much larger.
meillo@85	682 Whereas the code base changes would only slightly change on toggling
meillo@85	683 TLS or SASL support, it changed much on toggling POP support.
meillo@85	684 The changes in the code base could hardly be overviewed.
meillo@159	685 By having POP support togglable, a second code base had been created,
meillo@85	686 one that needed to be tested.
meillo@85	687 This situation is basically similar for the conditional TLS and SASL
meillo@85	688 code, but there the changes are minor and can yet be overviewed.
meillo@85	689 Still, conditional compilation of a code base creates variations
meillo@85	690 of the original program.
meillo@85	691 More variations require more testing and maintenance work.
meillo@85	692 .P
meillo@85	693 Two other options only specified default configuration values:
meillo@100	694 .Sw --with-mts
meillo@164	695 defined the default transport service.
meillo@85	696 .Ci f6aa95b724fd8c791164abe7ee5468bf5c34f226
meillo@85	697 With
meillo@100	698 .Sw --with-smtpservers
meillo@164	699 default SMTP servers could be specified.
meillo@72	700 .Ci 128545e06224233b7e91fc4c83f8830252fe16c9
meillo@164	701 Both of them became irrelevant when the SMTP transport service was removed.
meillo@164	702 .\" XXX code ref
meillo@164	703 In mmh, all messages are handed over to
meillo@164	704 .Pn sendmail
meillo@164	705 for transportation.
meillo@164	706
meillo@72	707
meillo@74	708 .U3 "Backup Prefix
meillo@74	709 .P
meillo@76	710 The backup prefix is the string that was prepended to message
meillo@76	711 filenames to tag them as deleted.
meillo@173	712 By default it had been the comma character (`\fL,\fP').
meillo@159	713 .\" XXX Zeitlich ordnen
meillo@78	714 In July 2000, Kimmo Suominen introduced
meillo@78	715 the configure option
meillo@78	716 .Sw --with-hash-backup
meillo@173	717 to change the default to the hash character `\f(CW#\fP'.
meillo@78	718 The choice was probably personal preference, because first, the
meillo@78	719 option was named
meillo@78	720 .Sw --with-backup-prefix.
meillo@173	721 and had the prefix character as argument.
meillo@173	722 But giving the hash character as argument caused too many problems
meillo@100	723 for Autoconf,
meillo@173	724 thus the option was limited to use the hash character as the default prefix.
meillo@100	725 This supports the assumption, that the choice for the hash was
meillo@100	726 personal preference only.
meillo@173	727 Being related or not, words that start with the hash character
meillo@78	728 introduce a comment in the Unix shell.
meillo@72	729 Thus, the command line
meillo@72	730 .Cl "rm #13 #15
meillo@72	731 calls
meillo@72	732 .Pn rm
meillo@173	733 without arguments because the first hash character starts the comment
meillo@72	734 that reaches until the end of the line.
meillo@72	735 To delete the backup files,
meillo@72	736 .Cl "rm ./#13 ./#15"
meillo@72	737 needs to be used.
meillo@100	738 Using the hash as backup prefix can be seen as a precaution against
meillo@78	739 data loss.
meillo@78	740 .P
meillo@159	741 First, I removed the configure option but added the profile entry
meillo@72	742 .Pe backup-prefix ,
meillo@72	743 which allows to specify an arbitrary string as backup prefix.
meillo@72	744 .Ci 6c40d481d661d532dd527eaf34cebb6d3f8ed086
meillo@76	745 Profile entries are the common method to change mmh's behavior.
meillo@76	746 This change did not remove the choice but moved it to a location where
meillo@72	747 it suited better.
meillo@76	748 .P
meillo@78	749 Eventually, however, the new trash folder concept
meillo@154	750 (cf. Sec.
meillo@154	751 .Cf trash-folder )
meillo@164	752 removed the need for the backup prefix completely.
meillo@78	753 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@133	754 .Ci ca0b3e830b86700d9e5e31b1784de2bdcaf58fc5
meillo@133	755
meillo@76	756
meillo@76	757 .U3 "Editor and Pager
meillo@74	758 .P
meillo@74	759 The two configure options
meillo@74	760 .CW --with-editor=EDITOR
meillo@74	761 .CW --with-pager=PAGER
meillo@74	762 were used to specify the default editor and pager at configure time.
meillo@109	763 Doing so at configure time made sense in the eighties,
meillo@76	764 when the set of available editors and pagers varied much across
meillo@76	765 different systems.
meillo@89	766 Today, the situation is more homogeneous.
meillo@74	767 The programs
meillo@74	768 .Pn vi
meillo@74	769 and
meillo@74	770 .Pn more
meillo@76	771 can be expected to be available on every Unix system,
meillo@74	772 as they are specified by POSIX since two decades.
meillo@74	773 (The specifications for
meillo@74	774 .Pn vi
meillo@74	775 and
meillo@74	776 .Pn more
meillo@74	777 appeared in
meillo@74	778 .[
meillo@74	779 posix 1987
meillo@74	780 .]
meillo@74	781 and,
meillo@74	782 .[
meillo@74	783 posix 1992
meillo@74	784 .]
meillo@74	785 respectively.)
meillo@74	786 As a first step, these two tools were hard-coded as defaults.
meillo@74	787 .Ci 5d43a99db70c12a673028c7758c20cbe3e13ef5f
meillo@74	788 Not changed were the
meillo@74	789 .Pe editor
meillo@74	790 and
meillo@74	791 .Pe moreproc
meillo@76	792 profile entries, which allowed the user to override the system defaults.
meillo@74	793 Later, the concept was reworked to respect the standard environment
meillo@74	794 variables
meillo@74	795 .Ev VISUAL
meillo@74	796 and
meillo@74	797 .Ev PAGER
meillo@76	798 if they are set.
meillo@74	799 Today, mmh determines the editor to use in the following order,
meillo@74	800 taking the first available and non-empty item:
meillo@171	801 .LI 1
meillo@74	802 Environment variable
meillo@74	803 .Ev MMHEDITOR
meillo@171	804 .LI 2
meillo@74	805 Profile entry
meillo@74	806 .Pe Editor
meillo@171	807 .LI 3
meillo@74	808 Environment variable
meillo@74	809 .Ev VISUAL
meillo@171	810 .LI 4
meillo@74	811 Environment variable
meillo@74	812 .Ev EDITOR
meillo@171	813 .LI 5
meillo@74	814 Command
meillo@74	815 .Pn vi .
meillo@171	816 .LP
meillo@76	817 .Ci f85f4b7ae62e3d05a945dcd46ead51f0a2a89a9b
meillo@76	818 .P
meillo@89	819 The pager to use is determined in a similar order,
meillo@74	820 also taking the first available and non-empty item:
meillo@171	821 .LI 1
meillo@74	822 Environment variable
meillo@74	823 .Ev MMHPAGER
meillo@171	824 .LI 2
meillo@74	825 Profile entry
meillo@74	826 .Pe Pager
meillo@74	827 (replaces
meillo@74	828 .Pe moreproc )
meillo@171	829 .LI 3
meillo@74	830 Environment variable
meillo@74	831 .Ev PAGER
meillo@171	832 .LI 4
meillo@74	833 Command
meillo@74	834 .Pn more .
meillo@171	835 .LP
meillo@74	836 .Ci 0c4214ea2aec6497d0d67b436bbee9bc1d225f1e
meillo@74	837 .P
meillo@76	838 By respecting the
meillo@74	839 .Ev VISUAL /\c
meillo@74	840 .Ev EDITOR
meillo@74	841 and
meillo@74	842 .Ev PAGER
meillo@76	843 environment variables,
meillo@76	844 the new behavior confirms better to the common style on Unix systems.
meillo@76	845 Additionally, the new approach is more uniform and clearer to users.
meillo@72	846
meillo@72	847
meillo@76	848 .U3 "ndbm
meillo@72	849 .P
meillo@74	850 .Pn slocal
meillo@78	851 used to depend on
meillo@74	852 .I ndbm ,
meillo@74	853 a database library.
meillo@76	854 The database is used to store the `\fLMessage-ID\fP's of all
meillo@76	855 messages delivered.
meillo@74	856 This enables
meillo@74	857 .Pn slocal
meillo@74	858 to suppress delivering the same message to the same user twice.
meillo@74	859 (This features was enabled by the
meillo@74	860 .Sw -suppressdup
meillo@74	861 switch.)
meillo@74	862 .P
meillo@100	863 A variety of versions of the database library exist.
meillo@78	864 .[
meillo@78	865 wolter unix incompat notes dbm
meillo@78	866 .]
meillo@74	867 Complicated autoconf code was needed to detect them correctly.
meillo@181	868 Furthermore, the configure switches
meillo@74	869 .Sw --with-ndbm=ARG
meillo@74	870 and
meillo@74	871 .Sw --with-ndbmheader=ARG
meillo@74	872 were added to help with difficult setups that would
meillo@78	873 not be detected automatically or correctly.
meillo@74	874 .P
meillo@74	875 By removing the suppress duplicates feature of
meillo@74	876 .Pn slocal ,
meillo@74	877 the dependency on
meillo@74	878 .I ndbm
meillo@78	879 vanished and 120 lines of complex autoconf code could be saved.
meillo@74	880 .Ci ecd6d6a20cb7a1507e3a20d6c4cb3a1cf14c6bbf
meillo@89	881 The change removed functionality too, but that is minor to the
meillo@78	882 improvement by dropping the dependency and the complex autoconf code.
meillo@159	883 .\" XXX argument: slocal ist sowieso nicht teil vom mmh kern
meillo@72	884
meillo@74	885 .U3 "mh-e Support
meillo@72	886 .P
meillo@74	887 The configure option
meillo@74	888 .Sw --disable-mhe
meillo@74	889 was removed when the mh-e support was reworked.
meillo@74	890 Mh-e is the Emacs front-end to MH.
meillo@76	891 It requires MH to provide minor additional functions.
meillo@76	892 The
meillo@76	893 .Sw --disable-mhe
meillo@76	894 configure option could switch these extensions off.
meillo@76	895 After removing the support for old versions of mh-e,
meillo@74	896 only the
meillo@74	897 .Sw -build
meillo@76	898 switches of
meillo@74	899 .Pn forw
meillo@74	900 and
meillo@74	901 .Pn repl
meillo@76	902 are left to be mh-e extensions.
meillo@76	903 They are now always built in because they add little code and complexity.
meillo@76	904 In consequence, the
meillo@74	905 .Sw --disable-mhe
meillo@76	906 configure option was removed
meillo@72	907 .Ci a7ce7b4a580d77b6c2c4d980812beb589aa4c643
meillo@74	908 Removing the option removed a second code setup that would have
meillo@74	909 needed to be tested.
meillo@159	910 .\" XXX datum?
meillo@169	911 This change was first accomplished in nmh and thereafter merged into mmh.
meillo@76	912 .P
meillo@76	913 The interface changes in mmh require mh-e to be adjusted in order
meillo@76	914 to be able to use mmh as back-end.
meillo@76	915 This will require minor changes to mh-e, but removing the
meillo@76	916 .Sw -build
meillo@76	917 switches would require more rework.
meillo@72	918
meillo@74	919 .U3 "Masquerading
meillo@72	920 .P
meillo@74	921 The configure option
meillo@74	922 .Sw --enable-masquerade
meillo@76	923 could take up to three arguments:
meillo@76	924 `draft_from', `mmailid', and `username_extension'.
meillo@74	925 They activated different types of address masquerading.
meillo@74	926 All of them were implemented in the SMTP-speaking
meillo@74	927 .Pn post
meillo@76	928 command, which provided an MSA.
meillo@76	929 Address masquerading is an MTA's task and mmh does not cover
meillo@76	930 this field anymore.
meillo@76	931 Hence, true masquerading needs to be implemented in the external MTA.
meillo@74	932 .P
meillo@74	933 The
meillo@74	934 .I mmailid
meillo@74	935 masquerading type is the oldest one of the three and the only one
meillo@74	936 available in the original MH.
meillo@74	937 It provided a
meillo@74	938 .I username
meillo@74	939 to
meillo@74	940 .I fakeusername
meillo@76	941 mapping, based on the password file's GECOS field.
meillo@74	942 The man page
meillo@181	943 .Mp mh-tailor (5)
meillo@74	944 described the use case as being the following:
meillo@98	945 .QS
meillo@74	946 This is useful if you want the messages you send to always
meillo@74	947 appear to come from the name of an MTA alias rather than your
meillo@74	948 actual account name. For instance, many organizations set up
meillo@74	949 `First.Last' sendmail aliases for all users. If this is
meillo@74	950 the case, the GECOS field for each user should look like:
meillo@74	951 ``First [Middle] Last <First.Last>''
meillo@98	952 .QE
meillo@74	953 .P
meillo@74	954 As mmh sends outgoing mail via the local MTA only,
meillo@76	955 the best location to do such global rewrites is there.
meillo@74	956 Besides, the MTA is conceptionally the right location because it
meillo@74	957 does the reverse mapping for incoming mail (aliasing), too.
meillo@181	958 Furthermore, masquerading set up there is readily available for all
meillo@74	959 mail software on the system.
meillo@76	960 Hence, mmailid masquerading was removed.
meillo@74	961 .Ci 0836c8000ccb34b59410ef1c15b1b7feac70ce5f
meillo@74	962 .P
meillo@74	963 The
meillo@74	964 .I username_extension
meillo@76	965 masquerading type did not replace the username but would append a suffix,
meillo@76	966 specified by the
meillo@74	967 .Ev USERNAME_EXTENSION
meillo@76	968 environment variable, to it.
meillo@76	969 This provided support for the
meillo@74	970 .I user-extension
meillo@74	971 feature of qmail and the similar
meillo@74	972 .I "plussed user
meillo@74	973 processing of sendmail.
meillo@74	974 The decision to remove this username_extension masquerading was
meillo@74	975 motivated by the fact that
meillo@74	976 .Pn spost
meillo@173	977 had not supported it already.
meillo@76	978 .Ci 2abae0bfd0ad5bf898461e50aa4b466d641f23d9
meillo@76	979 Username extensions are possible in mmh, but less convenient to use.
meillo@159	980 .\" XXX covered by next paragraph
meillo@76	981 .\" XXX format file %(getenv USERNAME_EXTENSION)
meillo@74	982 .P
meillo@74	983 The
meillo@74	984 .I draft_from
meillo@74	985 masquerading type instructed
meillo@74	986 .Pn post
meillo@84	987 to use the value of the
meillo@84	988 .Hd From
meillo@84	989 header field as SMTP envelope sender.
meillo@76	990 Sender addresses could be replaced completely.
meillo@74	991 .Ci b14ea6073f77b4359aaf3fddd0e105989db9
meillo@76	992 Mmh offers a kind of masquerading similar in effect, but
meillo@74	993 with technical differences.
meillo@76	994 As mmh does not transfer messages itself, the local MTA has final control
meillo@76	995 over the sender's address. Any masquerading mmh introduces may be reverted
meillo@76	996 by the MTA.
meillo@76	997 In times of pedantic spam checking, an MTA will take care to use
meillo@76	998 sensible envelope sender addresses to keep its own reputation up.
meillo@84	999 Nonetheless, the MUA can set the
meillo@84	1000 .Hd From
meillo@84	1001 header field and thereby propose
meillo@76	1002 a sender address to the MTA.
meillo@74	1003 The MTA may then decide to take that one or generate the canonical sender
meillo@74	1004 address for use as envelope sender address.
meillo@74	1005 .P
meillo@74	1006 In mmh, the MTA will always extract the recipient and sender from the
meillo@84	1007 message header (\c
meillo@74	1008 .Pn sendmail 's
meillo@74	1009 .Sw -t
meillo@74	1010 switch).
meillo@84	1011 The
meillo@84	1012 .Hd From
meillo@84	1013 header field of the draft may be set arbitrary by the user.
meillo@74	1014 If it is missing, the canonical sender address will be generated by the MTA.
meillo@74	1015
meillo@74	1016 .U3 "Remaining Options
meillo@74	1017 .P
meillo@74	1018 Two configure options remain in mmh.
meillo@74	1019 One is the locking method to use:
meillo@74	1020 .Sw --with-locking=[dot\|fcntl\|flock\|lockf] .
meillo@76	1021 The idea of removing all methods except the portable dot locking
meillo@76	1022 and having that one as the default is appealing, but this change
meillo@76	1023 requires deeper technical investigation into the topic.
meillo@76	1024 The other option,
meillo@74	1025 .Sw --enable-debug ,
meillo@74	1026 compiles the programs with debugging symbols and does not strip them.
meillo@74	1027 This option is likely to stay.
meillo@72	1028
meillo@72	1029
meillo@58	1030
meillo@63	1031
meillo@100	1032 .H2 "Command Line Switches
meillo@58	1033 .P
meillo@171	1034 The command line switches of MH tools is similar to the X Window style.
meillo@171	1035 .\" XXX ref
meillo@93	1036 They are words, introduced by a single dash.
meillo@93	1037 For example:
meillo@93	1038 .Cl "-truncate" .
meillo@93	1039 Every program in mmh has two generic switches:
meillo@93	1040 .Sw -help ,
meillo@93	1041 to print a short message on how to use the program, and
meillo@159	1042 .Sw -Version
meillo@164	1043 (with capital `V'), to tell what version of mmh the program belongs to.
meillo@93	1044 .P
meillo@93	1045 Switches change the behavior of programs.
meillo@93	1046 Programs that do one thing in one way require no switches.
meillo@93	1047 In most cases, doing something in exactly one way is too limiting.
meillo@97	1048 If there is basically one task to accomplish, but it should be done
meillo@93	1049 in various ways, switches are a good approach to alter the behavior
meillo@93	1050 of a program.
meillo@93	1051 Changing the behavior of programs provides flexibility and customization
meillo@97	1052 to users, but at the same time it complicates the code, documentation and
meillo@93	1053 usage of the program.
meillo@97	1054 .\" XXX: Ref
meillo@93	1055 Therefore, the number of switches should be kept small.
meillo@93	1056 A small set of well-chosen switches does no harm.
meillo@93	1057 But usually, the number of switches increases over time.
meillo@93	1058 Already in 1985, Rose and Romine have identified this as a major
meillo@93	1059 problem of MH:
meillo@93	1060 .[ [
meillo@93	1061 rose romine real work
meillo@93	1062 .], p. 12]
meillo@98	1063 .QS
meillo@93	1064 A complaint often heard about systems which undergo substantial development
meillo@93	1065 by many people over a number of years, is that more and more options are
meillo@93	1066 introduced which add little to the functionality but greatly increase the
meillo@93	1067 amount of information a user needs to know in order to get useful work done.
meillo@93	1068 This is usually referred to as creeping featurism.
meillo@93	1069 .QP
meillo@93	1070 Unfortunately MH, having undergone six years of off-and-on development by
meillo@93	1071 ten or so well-meaning programmers (the present authors included),
meillo@93	1072 suffers mightily from this.
meillo@98	1073 .QE
meillo@93	1074 .P
meillo@97	1075 Being reluctant to adding new switches \(en or `options',
meillo@97	1076 as Rose and Romine call them \(en is one part of a counter-action,
meillo@97	1077 the other part is removing hardly used switches.
meillo@97	1078 Nmh's tools had lots of switches already implemented,
meillo@97	1079 hence, cleaning up by removing some of them was the more important part
meillo@97	1080 of the counter-action.
meillo@93	1081 Removing existing functionality is always difficult because it
meillo@93	1082 breaks programs that use these functions.
meillo@93	1083 Also, for every obsolete feature, there'll always be someone who still
meillo@93	1084 uses it and thus opposes its removal.
meillo@93	1085 This puts the developer into the position,
meillo@93	1086 where sensible improvements to style are regarded as destructive acts.
meillo@97	1087 Yet, living with the featurism is far worse, in my eyes, because
meillo@97	1088 future needs will demand adding further features,
meillo@93	1089 worsening the situation more and more.
meillo@93	1090 Rose and Romine added in a footnote,
meillo@93	1091 ``[...]
meillo@93	1092 .Pn send
meillo@93	1093 will no doubt acquire an endless number of switches in the years to come.''
meillo@97	1094 Although clearly humorous, the comment points to the nature of the problem.
meillo@97	1095 Refusing to add any new switches would encounter the problem at its root,
meillo@97	1096 but this is not practical.
meillo@97	1097 New needs will require new switches and it would be unwise to block
meillo@97	1098 them strictly.
meillo@97	1099 Nevertheless, removing obsolete switches still is an effective approach
meillo@97	1100 to deal with the problem.
meillo@97	1101 Working on an experimental branch without an established user base,
meillo@97	1102 eased my work because I did not offend users when I removed existing
meillo@110	1103 functions.
meillo@93	1104 .P
meillo@93	1105 Rose and Romine counted 24 visible and 9 more hidden switches for
meillo@93	1106 .Pn send .
meillo@97	1107 In nmh, they increased up to 32 visible and 12 hidden ones.
meillo@182	1108 At the time of writing, no more than 4 visible switches and 1 hidden switch
meillo@97	1109 have remained in mmh's
meillo@97	1110 .Pn send .
meillo@183	1111 These numbers include two generic switches,
meillo@182	1112 .Sw -help
meillo@182	1113 and
meillo@183	1114 .Sw -Version .
meillo@183	1115 Hidden switches are ones not documented.
meillo@183	1116 In mmh, 12 tools have hidden switches.
meillo@183	1117 9 of them are
meillo@183	1118 .Sw -debug
meillo@183	1119 switches, the other 6 provide special interfaces for internal use.
meillo@93	1120 .P
meillo@154	1121 The figure displays the number of switches for each of the tools
meillo@159	1122 that is available in both nmh and mmh.
meillo@100	1123 The tools are sorted by the number of switches they had in nmh.
meillo@100	1124 Visible and hidden switches were counted,
meillo@97	1125 but not the generic help and version switches.
meillo@93	1126 Whereas in the beginning of the project, the average tool had 11 switches,
meillo@93	1127 now it has no more than 5 \(en only half as many.
meillo@93	1128 If the `no' switches and similar inverse variant are folded onto
meillo@100	1129 their counter-parts, the average tool had 8 switches in pre-mmh times and
meillo@100	1130 has 4 now.
meillo@93	1131 The total number of functional switches in mmh dropped from 465
meillo@182	1132 to 233.
meillo@58	1133
meillo@93	1134 .KS
meillo@93	1135 .in 1c
meillo@93	1136 .so input/switches.grap
meillo@93	1137 .KE
meillo@58	1138
meillo@93	1139 .P
meillo@93	1140 A part of the switches vanished after functions were removed.
meillo@93	1141 This was the case for network mail transfer, for instance.
meillo@97	1142 Sometimes, however, the work flow was the other way:
meillo@97	1143 I looked through the
meillo@97	1144 .Mp mh-chart (7)
meillo@97	1145 man page to identify the tools with apparently too many switches.
meillo@97	1146 Then considering the value of each of the switches by examining
meillo@97	1147 the tool's man page and source code, aided by recherche and testing.
meillo@97	1148 This way, the removal of functions was suggested by the aim to reduce
meillo@97	1149 the number of switches per command.
meillo@97	1150
meillo@58	1151
meillo@93	1152 .U3 "Draft Folder Facility
meillo@93	1153 .P
meillo@100	1154 A change early in the project was the complete transition from
meillo@93	1155 the single draft message to the draft folder facility.
meillo@97	1156 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@164	1157 .\" XXX ref to section ...
meillo@109	1158 The draft folder facility was introduced in the mid-eighties, when
meillo@100	1159 Rose and Romine called it a ``relatively new feature''.
meillo@93	1160 .[
meillo@93	1161 rose romine real work
meillo@93	1162 .]
meillo@110	1163 Since then, the facility had existed but was inactive by default.
meillo@93	1164 The default activation and the related rework of the tools made it
meillo@93	1165 possible to remove the
meillo@93	1166 .Sw -[no]draftfolder ,
meillo@93	1167 and
meillo@93	1168 .Sw -draftmessage
meillo@93	1169 switches from
meillo@93	1170 .Pn comp ,
meillo@93	1171 .Pn repl ,
meillo@93	1172 .Pn forw ,
meillo@93	1173 .Pn dist ,
meillo@93	1174 .Pn whatnow ,
meillo@93	1175 and
meillo@93	1176 .Pn send .
meillo@97	1177 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@97	1178 The only flexibility removed with this change is having multiple
meillo@97	1179 draft folders within one profile.
meillo@97	1180 I consider this a theoretical problem only.
meillo@159	1181 At the same time, the
meillo@93	1182 .Sw -draft
meillo@93	1183 switch of
meillo@93	1184 .Pn anno ,
meillo@93	1185 .Pn refile ,
meillo@93	1186 and
meillo@93	1187 .Pn send
meillo@93	1188 was removed.
meillo@159	1189 The special treatment of \fIthe\fP draft message became irrelevant after
meillo@93	1190 the rework of the draft system.
meillo@159	1191 (cf. Sec.
meillo@154	1192 .Cf draft-folder )
meillo@164	1193 Furthermore,
meillo@95	1194 .Pn comp
meillo@164	1195 no longer needs a
meillo@95	1196 .Sw -file
meillo@164	1197 switch as the draft folder facility together with the
meillo@95	1198 .Sw -form
meillo@164	1199 switch are sufficient.
meillo@93	1200
meillo@95	1201
meillo@102	1202 .U3 "In Place Editing
meillo@93	1203 .P
meillo@93	1204 .Pn anno
meillo@93	1205 had the switches
meillo@93	1206 .Sw -[no]inplace
meillo@100	1207 to either annotate the message in place and thus preserve hard links,
meillo@93	1208 or annotate a copy to replace the original message, breaking hard links.
meillo@97	1209 Following the assumption that linked messages should truly be the
meillo@97	1210 same message, and annotating it should not break the link, the
meillo@93	1211 .Sw -[no]inplace
meillo@93	1212 switches were removed and the previous default
meillo@93	1213 .Sw -inplace
meillo@93	1214 was made the only behavior.
meillo@97	1215 .Ci c8195849d2e366c569271abb0f5f60f4ebf0b4d0
meillo@93	1216 The
meillo@93	1217 .Sw -[no]inplace
meillo@93	1218 switches of
meillo@93	1219 .Pn repl ,
meillo@93	1220 .Pn forw ,
meillo@93	1221 and
meillo@93	1222 .Pn dist
meillo@93	1223 could be removed, too, as they were simply passed through to
meillo@93	1224 .Pn anno .
meillo@93	1225 .P
meillo@93	1226 .Pn burst
meillo@93	1227 also had
meillo@93	1228 .Sw -[no]inplace
meillo@95	1229 switches, but with different meaning.
meillo@95	1230 With
meillo@95	1231 .Sw -inplace ,
meillo@95	1232 the digest had been replaced by the table of contents (i.e. the
meillo@110	1233 introduction text) and the burst messages were placed right
meillo@95	1234 after this message, renumbering all following messages.
meillo@95	1235 Also, any trailing text of the digest was lost, though,
meillo@95	1236 in practice, it usually consists of an end-of-digest marker only.
meillo@95	1237 Nontheless, this behavior appeared less elegant than the
meillo@95	1238 .Sw -noinplace
meillo@95	1239 behavior, which already had been the default.
meillo@95	1240 Nmh's
meillo@95	1241 .Mp burst (1)
meillo@95	1242 man page reads:
meillo@98	1243 .QS
meillo@164	1244 If
meillo@164	1245 .Sw -noinplace
meillo@164	1246 is given, each digest is preserved, no table
meillo@93	1247 of contents is produced, and the messages contained within
meillo@93	1248 the digest are placed at the end of the folder. Other messages
meillo@93	1249 are not tampered with in any way.
meillo@98	1250 .QE
meillo@95	1251 .LP
meillo@93	1252 The decision to drop the
meillo@93	1253 .Sw -inplace
meillo@95	1254 behavior was supported by the code complexity and the possible data loss
meillo@95	1255 it caused.
meillo@93	1256 .Sw -noinplace
meillo@95	1257 was chosen to be the definitive behavior.
meillo@97	1258 .Ci 68a686adeb39223a5e1ad35e4a24890ec053679d
meillo@93	1259
meillo@95	1260
meillo@95	1261 .U3 "Forms and Format Strings
meillo@93	1262 .P
meillo@95	1263 Historically, the tools that had
meillo@95	1264 .Sw -form
meillo@95	1265 switches to supply a form file had
meillo@95	1266 .Sw -format
meillo@95	1267 switches as well to supply the contents of a form file as a string
meillo@95	1268 on the command line directly.
meillo@95	1269 In consequence, the following two lines equaled:
meillo@95	1270 .VS
meillo@95	1271 scan -form scan.mailx
meillo@95	1272 scan -format "`cat .../scan.mailx`"
meillo@95	1273 VE
meillo@95	1274 The
meillo@95	1275 .Sw -format
meillo@95	1276 switches were dropped in favor for extending the
meillo@95	1277 .Sw -form
meillo@95	1278 switches.
meillo@97	1279 .Ci f51956be123db66b00138f80464d06f030dbb88d
meillo@95	1280 If their argument starts with an equal sign (`='),
meillo@95	1281 then the rest of the argument is taken as a format string,
meillo@95	1282 otherwise the arguments is treated as the name of a format file.
meillo@95	1283 Thus, now the following two lines equal:
meillo@95	1284 .VS
meillo@95	1285 scan -form scan.mailx
meillo@95	1286 scan -form "=`cat .../scan.mailx`"
meillo@95	1287 VE
meillo@95	1288 This rework removed the prefix collision between
meillo@95	1289 .Sw -form
meillo@95	1290 and
meillo@95	1291 .Sw -format .
meillo@95	1292 Now, typing
meillo@95	1293 .Sw -fo
meillo@95	1294 suffices to specify form or format string.
meillo@95	1295 .P
meillo@95	1296 The different meaning of
meillo@95	1297 .Sw -format
meillo@95	1298 for
meillo@95	1299 .Pn repl
meillo@95	1300 and
meillo@95	1301 .Pn forw
meillo@95	1302 was removed in mmh.
meillo@95	1303 .Pn forw
meillo@95	1304 was completely switched to MIME-type forwarding, thus removing the
meillo@95	1305 .Sw -[no]format .
meillo@97	1306 .Ci 6e271608b7b9c23771523f88d23a4d3593010cf1
meillo@95	1307 For
meillo@95	1308 .Pn repl ,
meillo@95	1309 the
meillo@95	1310 .Sw -[no]format
meillo@95	1311 switches were reworked to
meillo@95	1312 .Sw -[no]filter
meillo@95	1313 switches.
meillo@97	1314 .Ci 67411b1f95d6ec987b4c732459e1ba8a8ac192c6
meillo@95	1315 The
meillo@95	1316 .Sw -format
meillo@95	1317 switches of
meillo@95	1318 .Pn send
meillo@95	1319 and
meillo@95	1320 .Pn post ,
meillo@95	1321 which had a third meaning,
meillo@95	1322 were removed likewise.
meillo@97	1323 .Ci f3cb7cde0e6f10451b6848678d95860d512224b9
meillo@95	1324 Eventually, the ambiguity of the
meillo@95	1325 .Sw -format
meillo@95	1326 switches was resolved by not anymore having any such switch in mmh.
meillo@95	1327
meillo@95	1328
meillo@95	1329 .U3 "MIME Tools
meillo@95	1330 .P
meillo@95	1331 The MIME tools, which were once part of
meillo@100	1332 .Pn mhn
meillo@164	1333 .\" XXX
meillo@164	1334 (whatever that stood for),
meillo@95	1335 had several switches that added little practical value to the programs.
meillo@95	1336 The
meillo@95	1337 .Sw -[no]realsize
meillo@95	1338 switches of
meillo@95	1339 .Pn mhbuild
meillo@95	1340 and
meillo@95	1341 .Pn mhlist
meillo@97	1342 were removed, doing real size calculations always now
meillo@97	1343 .Ci 8d8f1c3abc586c005c904e52c4adbfe694d2201c ,
meillo@159	1344 as nmh's
meillo@159	1345 .Mp mhbuild (1)
meillo@159	1346 man page states
meillo@95	1347 ``This provides an accurate count at the expense of a small delay.''
meillo@95	1348 This small delay is not noticable on modern systems.
meillo@95	1349 .P
meillo@95	1350 The
meillo@95	1351 .Sw -[no]check
meillo@95	1352 switches were removed together with the support for
meillo@95	1353 .Hd Content-MD5
meillo@95	1354 header fields.
meillo@95	1355 .[
meillo@95	1356 rfc 1864
meillo@95	1357 .]
meillo@97	1358 .Ci 31dc797eb5178970d68962ca8939da3fd9a8efda
meillo@154	1359 (cf. Sec.
meillo@154	1360 .Cf content-md5 )
meillo@95	1361 .P
meillo@95	1362 The
meillo@95	1363 .Sw -[no]ebcdicsafe
meillo@95	1364 and
meillo@95	1365 .Sw -[no]rfc934mode
meillo@95	1366 switches of
meillo@95	1367 .Pn mhbuild
meillo@95	1368 were removed because they are considered obsolete.
meillo@97	1369 .Ci 01a3480928da485b4d6109d36d751dfa71799d58
meillo@97	1370 .Ci 3363e2624dce0eb8164cf8b3f1ab385c8ff72e88
meillo@95	1371 .P
meillo@95	1372 Content caching of external MIME parts, activated with the
meillo@95	1373 .Sw -rcache
meillo@95	1374 and
meillo@95	1375 .Sw -wcache
meillo@95	1376 switches was completely removed.
meillo@97	1377 .Ci d1fefd9f614e4dc3cda16da6c69133c1b2005269
meillo@97	1378 External MIME parts are rare today, having a caching facility
meillo@159	1379 for them appears to be unnecessary.
meillo@95	1380 .P
meillo@95	1381 In pre-MIME times,
meillo@95	1382 .Pn mhl
meillo@95	1383 had covered many tasks that are part of MIME handling today.
meillo@95	1384 Therefore,
meillo@95	1385 .Pn mhl
meillo@95	1386 could be simplified to a large extend, reducing the number of its
meillo@95	1387 switches from 21 to 6.
meillo@97	1388 .Ci 350ad6d3542a07639213cf2a4fe524e829c1e7b6
meillo@97	1389 .Ci 0e46503be3c855bddaeae3843e1b659279c35d70
meillo@95	1390
meillo@95	1391
meillo@95	1392
meillo@95	1393
meillo@95	1394 .U3 "Header Printing
meillo@95	1395 .P
meillo@95	1396 .Pn folder 's
meillo@95	1397 data output is self-explaining enough that
meillo@159	1398 displaying the header line makes little sense.
meillo@95	1399 Hence, the
meillo@95	1400 .Sw -[no]header
meillo@95	1401 switch was removed and headers are never printed.
meillo@97	1402 .Ci 601cc73d1fa05ce96faa728f036d6c51b91701c7
meillo@95	1403 .P
meillo@95	1404 In
meillo@95	1405 .Pn mhlist ,
meillo@95	1406 the
meillo@95	1407 .Sw -[no]header
meillo@95	1408 switches were removed, too.
meillo@97	1409 .Ci b24f96523aaf60e44e04a3ffb1d22e69a13a602f
meillo@95	1410 But in this case headers are always printed,
meillo@95	1411 because the output is not self-explaining.
meillo@95	1412 .P
meillo@95	1413 .Pn scan
meillo@95	1414 also had
meillo@95	1415 .Sw -[no]header
meillo@95	1416 switches.
meillo@95	1417 Printing the header had been sensible until the introduction of
meillo@95	1418 format strings made it impossible to display the column headings.
meillo@95	1419 Only the folder name and the current date remained to be printed.
meillo@95	1420 As this information can be perfectly retrieved by
meillo@95	1421 .Pn folder
meillo@95	1422 and
meillo@95	1423 .Pn date ,
meillo@95	1424 consequently, the switches were removed.
meillo@97	1425 .Ci c477dc5d1d03fa6d9a8ab3dd3508c63cbddc044e
meillo@95	1426 .P
meillo@95	1427 By removing all
meillo@95	1428 .Sw -header
meillo@95	1429 switches, the collision with
meillo@95	1430 .Sw -help
meillo@95	1431 on the first two letters was resolved.
meillo@95	1432 Currently,
meillo@95	1433 .Sw -h
meillo@95	1434 evaluates to
meillo@95	1435 .Sw -help
meillo@95	1436 for all tools of mmh.
meillo@95	1437
meillo@95	1438
meillo@139	1439 .U3 "Suppressing Edits or the Invocation of the WhatNow Shell
meillo@95	1440 .P
meillo@95	1441 The
meillo@95	1442 .Sw -noedit
meillo@100	1443 switch of
meillo@95	1444 .Pn comp ,
meillo@95	1445 .Pn repl ,
meillo@95	1446 .Pn forw ,
meillo@95	1447 .Pn dist ,
meillo@95	1448 and
meillo@95	1449 .Pn whatnow
meillo@95	1450 was removed, but it can now be replaced by specifying
meillo@95	1451 .Sw -editor
meillo@95	1452 with an empty argument.
meillo@97	1453 .Ci 75fca31a5b9d5c1a99c74ab14c94438d8852fba9
meillo@95	1454 (Specifying
meillo@159	1455 .Cl "-editor /bin/true
meillo@95	1456 is nearly the same, only differing by the previous editor being set.)
meillo@95	1457 .P
meillo@95	1458 The more important change is the removal of the
meillo@95	1459 .Sw -nowhatnowproc
meillo@95	1460 switch.
meillo@97	1461 .Ci ee4f43cf2ef0084ec698e4e87159a94c01940622
meillo@95	1462 This switch had introduced an awkward behavior, as explained in nmh's
meillo@95	1463 man page for
meillo@95	1464 .Mp comp (1):
meillo@98	1465 .QS
meillo@164	1466 The
meillo@164	1467 .Sw -editor
meillo@164	1468 .Ar editor
meillo@164	1469 switch indicates the editor to use for
meillo@164	1470 the initial edit. Upon exiting from the editor,
meillo@164	1471 .Pn comp
meillo@164	1472 will invoke the
meillo@164	1473 .Pn whatnow
meillo@164	1474 program. See
meillo@164	1475 .Mp whatnow (1)
meillo@164	1476 for a discussion of available options.
meillo@164	1477 The invocation of this program can be
meillo@164	1478 inhibited by using the
meillo@164	1479 .Sw -nowhatnowproc
meillo@164	1480 switch. (In truth of fact, it is the
meillo@164	1481 .Pn whatnow
meillo@164	1482 program which starts the initial edit.
meillo@164	1483 Hence,
meillo@164	1484 .Sw -nowhatnowproc
meillo@164	1485 will prevent any edit from occurring.)
meillo@98	1486 .QE
meillo@95	1487 .P
meillo@95	1488 Effectively, the
meillo@95	1489 .Sw -nowhatnowproc
meillo@100	1490 switch creates only a draft message.
meillo@95	1491 As
meillo@159	1492 .Cl "-whatnowproc /bin/true
meillo@95	1493 causes the same behavior, the
meillo@95	1494 .Sw -nowhatnowproc
meillo@95	1495 switch was removed for being redundant.
meillo@100	1496 Likely, the
meillo@95	1497 .Sw -nowhatnowproc
meillo@100	1498 switch was intended to be used by front-ends.
meillo@95	1499
meillo@95	1500
meillo@95	1501
meillo@95	1502 .U3 "Various
meillo@95	1503 .BU
meillo@139	1504 With the removal of MMDF maildrop format support,
meillo@139	1505 .Pn packf
meillo@139	1506 and
meillo@139	1507 .Pn rcvpack
meillo@139	1508 no longer needed their
meillo@139	1509 .Sw -mbox
meillo@139	1510 and
meillo@139	1511 .Sw -mmdf
meillo@139	1512 switches.
meillo@139	1513 .Sw -mbox
meillo@154	1514 is the sole behavior now.
meillo@139	1515 .Ci 3916ab66ad5d183705ac12357621ea8661afd3c0
meillo@171	1516 Further rework in both tools made the
meillo@139	1517 .Sw -file
meillo@171	1518 switch unnecessary.
meillo@139	1519 .Ci ca1023716d4c2ab890696f3e41fa0d94267a940e
meillo@139	1520
meillo@139	1521 .BU
meillo@139	1522 Mmh's tools will no longer clear the screen (\c
meillo@139	1523 .Pn scan 's
meillo@139	1524 and
meillo@139	1525 .Pn mhl 's
meillo@139	1526 .Sw -[no]clear
meillo@139	1527 switches
meillo@139	1528 .Ci e57b17343dcb3ff373ef4dd089fbe778f0c7c270
meillo@139	1529 .Ci 943765e7ac5693ae177fd8d2b5a2440e53ce816e ).
meillo@139	1530 Neither will
meillo@139	1531 .Pn mhl
meillo@139	1532 ring the bell (\c
meillo@139	1533 .Sw -[no]bell
meillo@139	1534 .Ci e11983f44e59d8de236affa5b0d0d3067c192e24 )
meillo@139	1535 nor page the output itself (\c
meillo@139	1536 .Sw -length
meillo@139	1537 .Ci 5b9d883db0318ed2b84bb82dee880d7381f99188 ).
meillo@159	1538 .\" XXX Ref
meillo@139	1539 Generally, the pager to use is no longer specified with the
meillo@139	1540 .Sw -[no]moreproc
meillo@139	1541 command line switches for
meillo@139	1542 .Pn mhl
meillo@139	1543 and
meillo@139	1544 .Pn show /\c
meillo@139	1545 .Pn mhshow .
meillo@139	1546 .Ci 39e87a75b5c2d3572ec72e717720b44af291e88a
meillo@139	1547
meillo@139	1548 .BU
meillo@96	1549 In order to avoid prefix collisions among switch names, the
meillo@95	1550 .Sw -version
meillo@95	1551 switch was renamed to
meillo@95	1552 .Sw -Version
meillo@95	1553 (with capital `V').
meillo@97	1554 .Ci 32b2354dbaf4bf934936eb5b102a4a3d2fdd209a
meillo@95	1555 Every program has the
meillo@95	1556 .Sw -version
meillo@95	1557 switch but its first three letters collided with the
meillo@95	1558 .Sw -verbose
meillo@95	1559 switch, present in many programs.
meillo@95	1560 The rename solved this problem once for all.
meillo@95	1561 Although this rename breaks a basic interface, having the
meillo@95	1562 .Sw -V
meillo@95	1563 abbreviation to display the version information, isn't all too bad.
meillo@139	1564
meillo@95	1565 .BU
meillo@95	1566 .Sw -[no]preserve
meillo@95	1567 of
meillo@95	1568 .Pn refile
meillo@168	1569 was removed
meillo@168	1570 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@168	1571 because what use was it anyway?
meillo@168	1572 Quoting nmh's man page
meillo@165	1573 .Mp refile (1):
meillo@98	1574 .QS
meillo@95	1575 Normally when a message is refiled, for each destination
meillo@95	1576 folder it is assigned the number which is one above the current
meillo@95	1577 highest message number in that folder. Use of the
meillo@164	1578 .Sw -preserv
meillo@164	1579 [sic!] switch will override this message renaming, and try
meillo@95	1580 to preserve the number of the message. If a conflict for a
meillo@164	1581 particular folder occurs when using the
meillo@164	1582 .Sw -preserve
meillo@164	1583 switch, then
meillo@164	1584 .Pn refile
meillo@164	1585 will use the next available message number which
meillo@95	1586 is above the message number you wish to preserve.
meillo@98	1587 .QE
meillo@139	1588
meillo@95	1589 .BU
meillo@95	1590 The removal of the
meillo@95	1591 .Sw -[no]reverse
meillo@95	1592 switches of
meillo@95	1593 .Pn scan
meillo@97	1594 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@95	1595 is a bug fix, supported by the comments
meillo@95	1596 ``\-[no]reverse under #ifdef BERK (I really HATE this)''
meillo@95	1597 by Rose and
meillo@95	1598 ``Lists messages in reverse order with the `\-reverse' switch.
meillo@95	1599 This should be considered a bug.'' by Romine in the documentation.
meillo@159	1600 .\" XXX Ref: welche datei genau.
meillo@97	1601 The question remains why neither Rose and Romine had fixed this
meillo@109	1602 bug in the eighties when they wrote these comments nor has anyone
meillo@95	1603 thereafter.
meillo@93	1604
meillo@93	1605
meillo@93	1606 .ig
meillo@93	1607
meillo@95	1608 forw: [no]dashstuffing(mhl)
meillo@93	1609
meillo@95	1610 mhshow: [no]pause [no]serialonly
meillo@93	1611
meillo@93	1612 mhmail: resent queued
meillo@93	1613 inc: snoop, (pop)
meillo@93	1614
meillo@95	1615 mhl: [no]faceproc folder sleep
meillo@95	1616 [no]dashstuffing(forw) digest list volume number issue number
meillo@93	1617
meillo@95	1618 prompter: [no]doteof
meillo@93	1619
meillo@93	1620 refile: [no]preserve [no]unlink [no]rmmproc
meillo@93	1621
meillo@95	1622 send: [no]forward [no]mime [no]msgid
meillo@93	1623 [no]push split [no]unique (sasl) width snoop [no]dashstuffing
meillo@93	1624 attach attachformat
meillo@93	1625 whatnow: (noedit) attach
meillo@93	1626
meillo@93	1627 slocal: [no]suppressdups
meillo@93	1628
meillo@95	1629 spost: [no]filter [no]backup width [no]push idanno
meillo@93	1630 [no]check(whom) whom(whom)
meillo@93	1631
meillo@93	1632 whom: ???
meillo@93	1633
meillo@95	1634 ..
meillo@93	1635
meillo@93	1636
meillo@93	1637 .ig
meillo@93	1638
meillo@93	1639 .P
meillo@93	1640 In the best case, all switches are unambiguous on the first character,
meillo@93	1641 or on the three-letter prefix for the `no' variants.
meillo@96	1642 Reducing switch prefix collisions, shortens the necessary prefix length
meillo@93	1643 the user must type.
meillo@93	1644 Having less switches helps best.
meillo@93	1645
meillo@93	1646 ..
meillo@58	1647
meillo@95	1648
meillo@102	1649 .\" XXX: whatnow prompt commands
meillo@102	1650
meillo@102	1651
meillo@95	1652
meillo@95	1653
meillo@133	1654 .\" --------------------------------------------------------------
meillo@74	1655 .H1 "Modernizing
meillo@102	1656 .P
meillo@164	1657 In the more than thirty years of MH's existence, its code base was
meillo@159	1658 increasingly extended.
meillo@118	1659 New features entered the project and became alternatives to the
meillo@118	1660 existing behavior.
meillo@118	1661 Relicts from several decades have gathered in the code base,
meillo@118	1662 but seldom obsolete features were dropped.
meillo@118	1663 This section describes the removing of old code
meillo@118	1664 and the modernizing of the default setup.
meillo@118	1665 It focuses on the functional aspect only;
meillo@154	1666 the non-functional aspects of code style are discussed in Sec.
meillo@154	1667 .Cf code-style .
meillo@58	1668
meillo@58	1669
meillo@100	1670 .H2 "Code Relicts
meillo@0	1671 .P
meillo@159	1672 My position regarding the removal of obsolete functions of mmh,
meillo@159	1673 .\" XXX ``in order to remove old code,''
meillo@159	1674 is much more revolutional than the nmh community appreciates.
meillo@159	1675 Working on an experimental version, I was quickly able to drop
meillo@104	1676 functionality I considered ancient.
meillo@104	1677 The need for consensus with peers would have slowed this process down.
meillo@104	1678 Without the need to justify my decisions, I was able to rush forward.
meillo@110	1679 In December 2011, Paul Vixie motivated the nmh developers to just
meillo@159	1680 .\" XXX ugs
meillo@104	1681 do the work:
meillo@104	1682 .[
meillo@104	1683 paul vixie edginess nmh-workers
meillo@104	1684 .]
meillo@104	1685 .QS
meillo@104	1686 let's stop walking on egg shells with this code base. there's no need to
meillo@104	1687 discuss whether to keep using vfork, just note in [sic!] passing, [...]
meillo@104	1688 we don't need a separate branch for removing vmh
meillo@104	1689 or ridding ourselves of #ifdef's or removing posix replacement functions
meillo@164	1690 or depending on pure ansi/posix ``libc''.
meillo@104	1691 .QP
meillo@164	1692 these things should each be a day or two of work and the ``main branch''
meillo@104	1693 should just be modern. [...]
meillo@104	1694 let's push forward, aggressively.
meillo@104	1695 .QE
meillo@104	1696 .LP
meillo@104	1697 I did so already in the months before.
meillo@104	1698 I pushed forward.
meillo@159	1699 .\" XXX semicolon ?
meillo@104	1700 I simply dropped the cruft.
meillo@104	1701 .P
meillo@104	1702 The decision to drop a feature was based on literature research and
meillo@159	1703 careful thinking, but whether having had contact with this particular
meillo@104	1704 feature within my own computer life served as a rule of thumb.
meillo@159	1705 I explained my reasons in the commit messages
meillo@109	1706 in the version control system.
meillo@104	1707 Hence, others can comprehend my view and argue for undoing the change
meillo@104	1708 if I have missed an important aspect.
meillo@109	1709 I was quick in dropping parts.
meillo@179	1710 I rather include falsely dropped parts again, than going at a slower pace.
meillo@179	1711 Mmh is experimental work; it requires tough decisions.
meillo@159	1712 .\" XXX ``exp. work'' schon oft gesagt
meillo@12	1713
meillo@102	1714
meillo@104	1715 .U3 "Forking
meillo@12	1716 .P
meillo@109	1717 Being a tool chest, MH creates many processes.
meillo@104	1718 In earlier times
meillo@104	1719 .Fu fork()
meillo@104	1720 had been an expensive system call, because the process's image needed
meillo@159	1721 to be completely duplicated at once.
meillo@159	1722 This expensive work was especially unnecessary in the commonly occuring
meillo@159	1723 case wherein the image is replaced by a call to
meillo@104	1724 .Fu exec()
meillo@104	1725 right after having forked the child process.
meillo@104	1726 The
meillo@104	1727 .Fu vfork()
meillo@104	1728 system call was invented to speed up this particular case.
meillo@104	1729 It completely omits the duplication of the image.
meillo@104	1730 On old systems this resulted in significant speed ups.
meillo@104	1731 Therefore MH used
meillo@104	1732 .Fu vfork()
meillo@104	1733 whenever possible.
meillo@12	1734 .P
meillo@104	1735 Modern memory management units support copy-on-write semantics, which make
meillo@104	1736 .Fu fork()
meillo@104	1737 almost as fast as
meillo@104	1738 .Fu vfork() .
meillo@104	1739 The man page of
meillo@104	1740 .Mp vfork (2)
meillo@104	1741 in FreeBSD 8.0 states:
meillo@104	1742 .QS
meillo@104	1743 This system call will be eliminated when proper system sharing mechanisms
meillo@104	1744 are implemented. Users should not depend on the memory sharing semantics
meillo@104	1745 of vfork() as it will, in that case, be made synonymous to fork(2).
meillo@104	1746 .QE
meillo@104	1747 .LP
meillo@104	1748 Vixie supports the removal with the note that ``the last
meillo@104	1749 system on which fork was so slow that an mh user would notice it, was
meillo@104	1750 Eunice. that was 1987''.
meillo@104	1751 .[
meillo@104	1752 nmh-workers vixie edginess
meillo@104	1753 .]
meillo@104	1754 I replaced all calls to
meillo@104	1755 .Fu vfork()
meillo@104	1756 with calls to
meillo@104	1757 .Fu fork() .
meillo@109	1758 .Ci 40821f5c1316e9205a08375e7075909cc9968e7d
meillo@104	1759 .P
meillo@104	1760 Related to the costs of
meillo@104	1761 .Fu fork()
meillo@104	1762 is the probability of its success.
meillo@109	1763 In the eighties, on heavy loaded systems, calls to
meillo@104	1764 .Fu fork()
meillo@104	1765 were prone to failure.
meillo@104	1766 Hence, many of the
meillo@104	1767 .Fu fork()
meillo@104	1768 calls in the code were wrapped into loops to retry the
meillo@104	1769 .Fu fork()
meillo@159	1770 several times, to increase the chances to succeed, eventually.
meillo@109	1771 On modern systems, a failing
meillo@104	1772 .Fu fork()
meillo@109	1773 call is unusual.
meillo@104	1774 Hence, in the rare case when
meillo@104	1775 .Fu fork()
meillo@104	1776 fails, mmh programs simply abort.
meillo@109	1777 .Ci 5fbf37ee68e018998ada61eeab73e035b26834b6
meillo@12	1778
meillo@12	1779
meillo@109	1780 .U3 "Header Fields
meillo@104	1781 .BU
meillo@84	1782 The
meillo@84	1783 .Hd Encrypted
meillo@104	1784 header field was introduced by RFC\\|822,
meillo@109	1785 but already marked as legacy in RFC\\|2822.
meillo@109	1786 Today, OpenPGP provides the basis for standardized exchange of encrypted
meillo@104	1787 messages [RFC\\|4880, RFC\\|3156].
meillo@109	1788 Hence, the support for
meillo@104	1789 .Hd Encrypted
meillo@104	1790 header fields is removed in mmh.
meillo@109	1791 .Ci 064527f7b57ab050e5af13e15ad99aeeab125857
meillo@104	1792 .BU
meillo@159	1793 The native support for
meillo@84	1794 .Hd Face
meillo@104	1795 header fields has been removed, as well.
meillo@109	1796 .Ci 8e5be81f784682822f5e868c1bf3c8624682bd23
meillo@104	1797 This feature is similar to the
meillo@84	1798 .Hd X-Face
meillo@84	1799 header field in its intent,
meillo@21	1800 but takes a different approach to store the image.
meillo@84	1801 Instead of encoding the image data directly into the header field,
meillo@109	1802 it contains the hostname and UDP port where the image
meillo@109	1803 date can be retrieved.
meillo@159	1804 There is even a third Face system,
meillo@109	1805 which is the successor of
meillo@109	1806 .Hd X-Face ,
meillo@109	1807 although it re-uses the
meillo@104	1808 .Hd Face
meillo@109	1809 header field.
meillo@109	1810 It was invented in 2005 and supports colored PNG images.
meillo@104	1811 None of the Face systems described here is popular today.
meillo@104	1812 Hence, mmh has no direct support for them.
meillo@104	1813 .BU
meillo@154	1814 .Id content-md5
meillo@104	1815 The
meillo@104	1816 .Hd Content-MD5
meillo@104	1817 header field was introduced by RFC\\|1864.
meillo@104	1818 It provides detection of data corruption during the transfer.
meillo@104	1819 But it can not ensure verbatim end-to-end delivery of the contents
meillo@104	1820 [RFC\\|1864].
meillo@104	1821 The proper approach to verify content integrity in an
meillo@166	1822 end-to-end relationship is the use of digital signatures.
meillo@104	1823 .\" XXX (RFCs FIXME).
meillo@104	1824 On the other hand, transfer protocols should detect corruption during
meillo@109	1825 the transmission.
meillo@109	1826 The TCP includes a checksum field therefore.
meillo@104	1827 These two approaches in combinations render the
meillo@104	1828 .Hd Content-MD5
meillo@104	1829 header field superfluous.
meillo@109	1830 Not a single one out of 4\\|200 messages from two decades
meillo@109	1831 in an nmh-workers mailing list archive contains a
meillo@104	1832 .Hd Content-MD5
meillo@104	1833 header field.
meillo@104	1834 Neither did any of the 60\\|000 messages in my personal mail storage.
meillo@104	1835 Removing the support for this header field,
meillo@104	1836 removed the last place where MD5 computation was needed.
meillo@109	1837 .Ci 31dc797eb5178970d68962ca8939da3fd9a8efda
meillo@104	1838 Hence, the MD5 code could be removed as well.
meillo@104	1839 Over 500 lines of code vanished by this one change.
meillo@104	1840
meillo@104	1841
meillo@104	1842 .U3 "MMDF maildrop support
meillo@21	1843 .P
meillo@104	1844 This type of format is conceptionally similar to the mbox format,
meillo@139	1845 but uses a different message delimiter (`\fL\\1\\1\\1\\1\fP',
meillo@139	1846 commonly written as `\fL^A^A^A^A\fP', instead of `\fLFrom\0\fP').
meillo@104	1847 Mbox is the de-facto standard maildrop format on Unix,
meillo@159	1848 whereas the MMDF maildrop format is now forgotten.
meillo@159	1849 By dropping the MMDF maildrop format support,
meillo@159	1850 mbox became the only packed mailbox format supported in mmh.
meillo@104	1851 .P
meillo@109	1852 The simplifications within the code were moderate.
meillo@109	1853 Mainly, the reading and writing of MMDF mailbox files was removed.
meillo@109	1854 But also, switches of
meillo@109	1855 .Pn packf
meillo@104	1856 and
meillo@109	1857 .Pn rcvpack
meillo@109	1858 could be removed.
meillo@109	1859 .Ci 3916ab66ad5d183705ac12357621ea8661afd3c0
meillo@109	1860 In the message parsing function
meillo@109	1861 .Fn sbr/m_getfld.c ,
meillo@109	1862 knowledge of MMDF packed mail boxes was removed.
meillo@109	1863 .Ci 684ec30d81e1223a282764452f4902ed4ad1c754
meillo@109	1864 Further code structure simplifications may be possible there,
meillo@109	1865 because only one single packed mailbox format is left to be supported.
meillo@104	1866 I have not worked on them yet because
meillo@104	1867 .Fu m_getfld()
meillo@104	1868 is heavily optimized and thus dangerous to touch.
meillo@104	1869 The risk of damaging the intricate workings of the optimized code is
meillo@104	1870 too high.
meillo@104	1871
meillo@12	1872
meillo@101	1873 .U3 "Prompter's Control Keys
meillo@20	1874 .P
meillo@20	1875 The program
meillo@20	1876 .Pn prompter
meillo@104	1877 queries the user to fill in a message form.
meillo@104	1878 When used by
meillo@20	1879 .Pn comp
meillo@104	1880 as
meillo@104	1881 .Cl "comp -editor prompter" ,
meillo@20	1882 the resulting behavior is similar to
meillo@20	1883 .Pn mailx .
meillo@51	1884 Apparently,
meillo@20	1885 .Pn prompter
meillo@173	1886 had not been touched lately.
meillo@104	1887 Otherwise it's hardly explainable why it
meillo@20	1888 still offered the switches
meillo@84	1889 .Sw -erase
meillo@84	1890 .Ar chr
meillo@20	1891 and
meillo@84	1892 .Sw -kill
meillo@84	1893 .Ar chr
meillo@20	1894 to name the characters for command line editing.
meillo@21	1895 The times when this had been necessary are long time gone.
meillo@20	1896 Today these things work out-of-the-box, and if not, are configured
meillo@20	1897 with the standard tool
meillo@20	1898 .Pn stty .
meillo@104	1899 The switches are removed now
meillo@104	1900 .Ci 0bd9750710cdbab80cfb4036dd87af20afe1552f .
meillo@20	1901
meillo@104	1902
meillo@109	1903 .U3 "Hardcopy Terminal Support
meillo@21	1904 .P
meillo@109	1905 More of a funny anecdote is a check for being connected to a
meillo@109	1906 hardcopy terminal.
meillo@159	1907 It remained in the code until spring 2012, when I finally removed it
meillo@104	1908 .Ci b7764c4a6b71d37918a97594d866258f154017ca .
meillo@21	1909 .P
meillo@109	1910 The check only prevented a pager to be placed between the printing
meillo@104	1911 program (\c
meillo@104	1912 .Pn mhl )
meillo@104	1913 and the terminal.
meillo@109	1914 In nmh, this could have been ensured statically with the
meillo@104	1915 .Sw -nomoreproc
meillo@109	1916 at the command line, too.
meillo@121	1917 In mmh, setting the profile entry
meillo@104	1918 .Pe Pager
meillo@104	1919 or the environment variable
meillo@104	1920 .Ev PAGER
meillo@104	1921 to
meillo@109	1922 .Pn cat
meillo@159	1923 is sufficient.
meillo@104	1924
meillo@104	1925
meillo@21	1926
meillo@12	1927
meillo@58	1928 .H2 "Attachments
meillo@22	1929 .P
meillo@101	1930 The mind model of email attachments is unrelated to MIME.
meillo@101	1931 Although the MIME RFCs (2045 through 2049) define the technical
meillo@109	1932 requirements for having attachments, they do not mention the word
meillo@181	1933 attachment.
meillo@101	1934 Instead of attachments, MIME talks about ``multi-part message bodies''
meillo@101	1935 [RFC\\|2045], a more general concept.
meillo@101	1936 Multi-part messages are messages
meillo@101	1937 ``in which one or more different
meillo@101	1938 sets of data are combined in a single body''
meillo@101	1939 [RFC\\|2046].
meillo@101	1940 MIME keeps its descriptions generic;
meillo@101	1941 it does not imply specific usage models.
meillo@109	1942 One usage model became prevalent: attachments.
meillo@101	1943 The idea is having a main text document with files of arbitrary kind
meillo@101	1944 attached to it.
meillo@101	1945 In MIME terms, this is a multi-part message having a text part first
meillo@110	1946 and parts of arbitrary type following.
meillo@101	1947 .P
meillo@101	1948 MH's MIME support is a direct implementation of the RFCs.
meillo@101	1949 The perception of the topic described in the RFCs is clearly visible
meillo@101	1950 in MH's implementation.
meillo@159	1951 .\" XXX rewrite ``no idea''.
meillo@159	1952 As a result,
meillo@159	1953 MH had all the MIME features but no idea of attachments.
meillo@173	1954 But users do not need all the MIME features,
meillo@109	1955 they want convenient attachment handling.
meillo@109	1956
meillo@102	1957
meillo@102	1958 .U3 "Composing MIME Messages
meillo@102	1959 .P
meillo@102	1960 In order to improve the situation on the message composing side,
meillo@102	1961 Jon Steinhart had added an attachment system to nmh in 2002.
meillo@101	1962 .Ci 7480dbc14bc90f2d872d434205c0784704213252
meillo@102	1963 In the file
meillo@102	1964 .Fn docs/README-ATTACHMENTS ,
meillo@102	1965 he described his motivation to do so as such:
meillo@101	1966 .QS
meillo@159	1967 Although nmh contains the necessary functionality for MIME message
meillo@159	1968 handing [sic!], the interface to this functionality is pretty obtuse.
meillo@101	1969 There's no way that I'm ever going to convince my partner to write
meillo@101	1970 .Pn mhbuild
meillo@101	1971 composition files!
meillo@101	1972 .QE
meillo@102	1973 .LP
meillo@102	1974 With this change, the mind model of attachments entered nmh.
meillo@102	1975 In the same document:
meillo@101	1976 .QS
meillo@101	1977 These changes simplify the task of managing attachments on draft files.
meillo@101	1978 They allow attachments to be added, listed, and deleted.
meillo@101	1979 MIME messages are automatically created when drafts with attachments
meillo@101	1980 are sent.
meillo@101	1981 .QE
meillo@102	1982 .LP
meillo@102	1983 Unfortunately, the attachment system,
meillo@102	1984 like any new facilities in nmh,
meillo@110	1985 was inactive by default.
meillo@101	1986 .P
meillo@101	1987 During my work in Argentina, I tried to improve the attachment system.
meillo@102	1988 But, because of great opposition in the nmh community,
meillo@102	1989 my patch died as a proposal on the mailing list, after long discussions.
meillo@101	1990 .[
meillo@101	1991 nmh-workers attachment proposal
meillo@101	1992 .]
meillo@110	1993 In January 2012, I extended the patch and applied it to mmh.
meillo@101	1994 .Ci 8ff284ff9167eff8f5349481529332d59ed913b1
meillo@102	1995 In mmh, the attachment system is active by default.
meillo@102	1996 Instead of command line switches, the
meillo@102	1997 .Pe Attachment-Header
meillo@102	1998 profile entry is used to specify
meillo@102	1999 the name of the attachment header field.
meillo@102	2000 It is pre-defined to
meillo@102	2001 .Hd Attach .
meillo@101	2002 .P
meillo@159	2003 To add an attachment to a draft, a header line needs to be added:
meillo@101	2004 .VS
meillo@101	2005 To: bob
meillo@101	2006 Subject: The file you wanted
meillo@101	2007 Attach: /path/to/the/file-bob-wanted
meillo@101	2008 --------
meillo@101	2009 Here it is.
meillo@101	2010 VE
meillo@101	2011 The header field can be added to the draft manually in the editor,
meillo@102	2012 or by using the `attach' command at the WhatNow prompt, or
meillo@102	2013 non-interactively with
meillo@101	2014 .Pn anno :
meillo@101	2015 .VS
meillo@102	2016 anno -append -nodate -component Attach -text /path/to/attachment
meillo@101	2017 VE
meillo@102	2018 Drafts with attachment headers are converted to MIME automatically by
meillo@102	2019 .Pn send .
meillo@102	2020 The conversion to MIME is invisible to the user.
meillo@159	2021 The draft stored in the draft folder is always in source form with
meillo@101	2022 attachment headers.
meillo@179	2023 If the MIMEification fails (e.g. because the file to attach
meillo@179	2024 is not accessible) the original draft is not changed.
meillo@101	2025 .P
meillo@102	2026 The attachment system handles the forwarding of messages, too.
meillo@173	2027 If the attachment header value starts with a plus character (`\fL+\fP'),
meillo@101	2028 like in
meillo@101	2029 .Cl "Attach: +bob 30 42" ,
meillo@159	2030 the given messages in the specified folder will be attached.
meillo@101	2031 This allowed to simplify
meillo@101	2032 .Pn forw .
meillo@101	2033 .Ci f41f04cf4ceca7355232cf7413e59afafccc9550
meillo@101	2034 .P
meillo@101	2035 Closely related to attachments is non-ASCII text content,
meillo@101	2036 because it requires MIME too.
meillo@102	2037 In nmh, the user needed to call `mime' at the WhatNow prompt
meillo@101	2038 to have the draft converted to MIME.
meillo@102	2039 This was necessary whenever the draft contained non-ASCII characters.
meillo@101	2040 If the user did not call `mime', a broken message would be sent.
meillo@101	2041 Therefore, the
meillo@101	2042 .Pe automimeproc
meillo@101	2043 profile entry could be specified to have the `mime' command invoked
meillo@102	2044 automatically each time.
meillo@179	2045 Unfortunately, this approach conflicted with the attachment system
meillo@101	2046 because the draft would already be in MIME format at the time
meillo@101	2047 when the attachment system wanted to MIMEify it.
meillo@102	2048 To use nmh's attachment system, `mime' must not be called at the
meillo@102	2049 WhatNow prompt and
meillo@101	2050 .Pe automimeproc
meillo@102	2051 must not be set in the profile.
meillo@101	2052 But then the case of non-ASCII text without attachment headers was
meillo@101	2053 not caught.
meillo@102	2054 All in all, the solution was complex and irritating.
meillo@168	2055 My patch from December 2010
meillo@168	2056 .[
meillo@168	2057 nmh-workers attachment proposal
meillo@168	2058 .]
meillo@168	2059 would have simplified the situation.
meillo@102	2060 .P
meillo@101	2061 Mmh's current solution is even more elaborate.
meillo@101	2062 Any necessary MIMEification is done automatically.
meillo@101	2063 There is no `mime' command at the WhatNow prompt anymore.
meillo@102	2064 The draft will be converted automatically to MIME when either an
meillo@102	2065 attachment header or non-ASCII text is present.
meillo@173	2066 Furthermore, the hash character (`\fL#\fP') is not special any more
meillo@159	2067 at line beginnings in the draft message.
meillo@159	2068 .\" XXX REF ?
meillo@159	2069 Users need not concern themselves with the whole topic at all.
meillo@101	2070 .P
meillo@102	2071 Although the new approach does not anymore support arbitrary MIME
meillo@102	2072 compositions directly, the full power of
meillo@101	2073 .Pn mhbuild
meillo@101	2074 can still be accessed.
meillo@102	2075 Given no attachment headers are included, the user can create
meillo@101	2076 .Pn mhbuild
meillo@102	2077 composition drafts like in nmh.
meillo@101	2078 Then, at the WhatNow prompt, he needs to invoke
meillo@101	2079 .Cl "edit mhbuild
meillo@101	2080 to convert it to MIME.
meillo@110	2081 Because the resulting draft does neither contain non-ASCII characters
meillo@102	2082 nor has it attachment headers, the attachment system will not touch it.
meillo@101	2083 .P
meillo@159	2084 The approach taken in mmh is tailored towards today's most common case:
meillo@159	2085 a text part, possibly with attachments.
meillo@159	2086 This case was simplified.
meillo@102	2087
meillo@112	2088
meillo@102	2089 .U3 "MIME Type Guessing
meillo@102	2090 .P
meillo@159	2091 From the programmer's point of view, the use of
meillo@101	2092 .Pn mhbuild
meillo@159	2093 composition drafts had one notable advantage over attachment headers:
meillo@159	2094 The user provides the appropriate MIME types for files to include.
meillo@102	2095 The attachment system needs to find out the correct MIME type itself.
meillo@102	2096 This is a difficult task, yet it spares the user irritating work.
meillo@102	2097 Determining the correct MIME type of content is partly mechanical,
meillo@102	2098 partly intelligent work.
meillo@102	2099 Forcing the user to find out the correct MIME type,
meillo@102	2100 forces him to do partly mechanical work.
meillo@179	2101 Letting the computer do the work can lead to bad choices for difficult
meillo@102	2102 content.
meillo@102	2103 For mmh, the latter option was chosen.
meillo@102	2104 .P
meillo@102	2105 Determining the MIME type by the suffix of the file name is a dumb
meillo@102	2106 approach, yet it is simple to implement and provides good results
meillo@102	2107 for the common cases.
meillo@102	2108 Mmh implements this approach in the
meillo@102	2109 .Pn print-mimetype
meillo@102	2110 script.
meillo@112	2111 .Ci 4b5944268ea0da7bb30598a27857304758ea9b44
meillo@102	2112 Using it is the default choice.
meillo@102	2113 .P
meillo@112	2114 A far better, though less portable, approach is the use of
meillo@102	2115 .Pn file .
meillo@102	2116 This standard tool tries to determine the type of files.
meillo@102	2117 Unfortunately, its capabilities and accuracy varies from system to system.
meillo@102	2118 Additionally, its output was only intended for human beings,
meillo@102	2119 but not to be used by programs.
meillo@102	2120 It varies much.
meillo@102	2121 Nevertheless, modern versions of GNU
meillo@102	2122 .Pn file ,
meillo@102	2123 which is prevalent on the popular GNU/Linux systems,
meillo@159	2124 provide MIME type output in machine-readable form.
meillo@102	2125 Although this solution is highly system-dependent,
meillo@102	2126 it solves the difficult problem well.
meillo@102	2127 On systems where GNU
meillo@102	2128 .Pn file ,
meillo@102	2129 version 5.04 or higher, is available it should be used.
meillo@102	2130 One needs to specify the following profile entry to do so:
meillo@112	2131 .Ci 3baec236a39c5c89a9bda8dbd988d643a21decc6
meillo@102	2132 .VS
meillo@102	2133 Mime-Type-Query: file -b --mime
meillo@102	2134 VE
meillo@102	2135 .LP
meillo@102	2136 Other versions of
meillo@102	2137 .Pn file
meillo@102	2138 might possibly be usable with wrapper scripts to reformat the output.
meillo@102	2139 The diversity among
meillo@102	2140 .Pn file
meillo@102	2141 implementations is great; one needs to check the local variant.
meillo@102	2142 .P
meillo@102	2143 If no MIME type can be determined, text content gets sent as
meillo@102	2144 `text/plain' and anything else under the generic fall-back type
meillo@102	2145 `application/octet-stream'.
meillo@102	2146 It is not possible in mmh to override the automatic MIME type guessing
meillo@102	2147 for a specific file.
meillo@159	2148 To do so, either the user would need to know in advance for which file
meillo@159	2149 the automatic guessing fails, or the system would require interaction.
meillo@102	2150 I consider both cases impractical.
meillo@102	2151 The existing solution should be sufficient.
meillo@102	2152 If not, the user may always fall back to
meillo@102	2153 .Pn mhbuild
meillo@102	2154 composition drafts and ignore the attachment system.
meillo@101	2155
meillo@102	2156
meillo@102	2157 .U3 "Storing Attachments
meillo@102	2158 .P
meillo@169	2159 Extracting MIME parts of a message and storing them to disk is performed by
meillo@108	2160 .Pn mhstore .
meillo@108	2161 The program has two operation modes,
meillo@108	2162 .Sw -auto
meillo@108	2163 and
meillo@108	2164 .Sw -noauto .
meillo@108	2165 With the former one, each part is stored under the filename given in the
meillo@108	2166 MIME part's meta information, if available.
meillo@108	2167 This naming information is usually available for modern attachments.
meillo@108	2168 If no filename is available, this MIME part is stored as if
meillo@108	2169 .Sw -noauto
meillo@108	2170 would have been specified.
meillo@108	2171 In the
meillo@108	2172 .Sw -noauto
meillo@108	2173 mode, the parts are processed according to rules, defined by
meillo@108	2174 .Pe mhstore-store-*
meillo@108	2175 profile entries.
meillo@108	2176 These rules define generic filename templates for storing
meillo@108	2177 or commands to post-process the contents in arbitrary ways.
meillo@108	2178 If no matching rule is available the part is stored under a generic
meillo@108	2179 filename, built from message number, MIME part number, and MIME type.
meillo@108	2180 .P
meillo@108	2181 The
meillo@108	2182 .Sw -noauto
meillo@108	2183 mode had been the default in nmh because it was considered safe,
meillo@108	2184 in contrast to the
meillo@108	2185 .Sw -auto
meillo@108	2186 mode.
meillo@108	2187 In mmh,
meillo@108	2188 .Sw -auto
meillo@108	2189 is not dangerous anymore.
meillo@108	2190 Two changes were necessary:
meillo@171	2191 .LI 1
meillo@108	2192 Any directory path is removed from the proposed filename.
meillo@108	2193 Thus, the files are always stored in the expected directory.
meillo@108	2194 .Ci 41b6eadbcecf63c9a66aa5e582011987494abefb
meillo@171	2195 .LI 2
meillo@108	2196 Tar files are not extracted automatically any more.
meillo@108	2197 Thus, the rest of the file system will not be touched.
meillo@108	2198 .Ci 94c80042eae3383c812d9552089953f9846b1bb6
meillo@108	2199 .LP
meillo@108	2200 Now, the outcome of mmh's
meillo@108	2201 .Cl "mhstore -auto
meillo@110	2202 can be foreseen from the output of
meillo@108	2203 .Cl "mhlist -verbose" .
meillo@108	2204 .P
meillo@108	2205 The
meillo@108	2206 .Sw -noauto
meillo@108	2207 mode is seen to be more powerful but less convenient.
meillo@108	2208 On the other hand,
meillo@108	2209 .Sw -auto
meillo@108	2210 is safe now and
meillo@108	2211 storing attachments under their original name is intuitive.
meillo@108	2212 Hence,
meillo@108	2213 .Sw -auto
meillo@108	2214 serves better as the default option.
meillo@108	2215 .Ci 3410b680416c49a7617491af38bc1929855a331d
meillo@108	2216 .P
meillo@108	2217 Files are stored into the directory given by the
meillo@108	2218 .Pe Nmh-Storage
meillo@108	2219 profile entry, if set, or
meillo@108	2220 into the current working directory, otherwise.
meillo@108	2221 Storing to different directories is only possible with
meillo@108	2222 .Pe mhstore-store-*
meillo@108	2223 profile entries.
meillo@108	2224 .P
meillo@108	2225 Still, in both modes, existing files get overwritten silently.
meillo@108	2226 This can be considered a bug.
meillo@108	2227 Yet, each other behavior has its draw-backs, too.
meillo@108	2228 Refusing to replace files requires adding a
meillo@108	2229 .Sw -force
meillo@108	2230 option.
meillo@108	2231 Users will likely need to invoke
meillo@108	2232 .Pn mhstore
meillo@108	2233 a second time with
meillo@159	2234 .Sw -force .
meillo@159	2235 Eventually, only the user can decide in the specific case.
meillo@108	2236 This requires interaction, which I like to avoid if possible.
meillo@108	2237 Appending a unique suffix to the filename is another bad option.
meillo@108	2238 For now, the behavior remains as it is.
meillo@108	2239 .P
meillo@108	2240 In mmh, only MIME parts of type message are special in
meillo@108	2241 .Pn mhstore 's
meillo@108	2242 .Sw -auto
meillo@108	2243 mode.
meillo@108	2244 Instead of storing message/rfc822 parts as files to disk,
meillo@108	2245 they are stored as messages into the current mail folder.
meillo@159	2246 The same applies to message/partial, although the parts are
meillo@159	2247 automatically reassembled beforehand.
meillo@159	2248 MIME parts of type message/external-body are not automatically retrieved
meillo@159	2249 anymore.
meillo@159	2250 Instead, information on how to retrieve them is output.
meillo@108	2251 Not supporting this rare case saved nearly one thousand lines of code.
meillo@108	2252 .Ci 55e1d8c654ee0f7c45b9361ce34617983b454c32
meillo@108	2253 .\" XXX mention somewhere else too: (The profile entry `nmh-access-ftp'
meillo@108	2254 .\" and sbr/ruserpass.c for reading ~/.netrc are gone now.)
meillo@159	2255 `application/octet-stream; type=tar' is not special anymore.
meillo@108	2256 Automatically extracting such MIME parts had been the dangerous part
meillo@108	2257 of the
meillo@108	2258 .Sw -auto
meillo@108	2259 mode.
meillo@108	2260 .Ci 94c80042eae3383c812d9552089953f9846b1bb6
meillo@108	2261
meillo@102	2262
meillo@102	2263
meillo@102	2264 .U3 "Showing MIME Messages
meillo@102	2265 .P
meillo@114	2266 The program
meillo@114	2267 .Pn mhshow
meillo@114	2268 had been written to display MIME messages.
meillo@114	2269 It implemented the conceptional view of the MIME RFCs.
meillo@114	2270 Nmh's
meillo@114	2271 .Pn mhshow
meillo@114	2272 handled each MIME part independently, presenting them separately
meillo@114	2273 to the user.
meillo@114	2274 This does not match today's understanding of email attachments,
meillo@114	2275 where displaying a message is seen to be a single, integrated operation.
meillo@114	2276 Today, email messages are expected to consist of a main text part
meillo@114	2277 plus possibly attachments.
meillo@114	2278 They are not any more seen to be arbitrary MIME hierarchies with
meillo@114	2279 information on how to display the individual parts.
meillo@114	2280 I adjusted
meillo@114	2281 .Pn mhshow 's
meillo@114	2282 behavior to the modern view on the topic.
meillo@114	2283 .P
meillo@159	2284 One should note that this section completely ignores the original
meillo@114	2285 .Pn show
meillo@114	2286 program, because it was not capable to display MIME messages
meillo@114	2287 and is no longer part of mmh.
meillo@179	2288 .\" XXX ref to other section
meillo@114	2289 Although
meillo@114	2290 .Pn mhshow
meillo@114	2291 was renamed to
meillo@114	2292 .Pn show
meillo@114	2293 in mmh, this section uses the name
meillo@114	2294 .Pn mhshow ,
meillo@114	2295 in order to avoid confusion.
meillo@114	2296 .P
meillo@114	2297 In mmh, the basic idea is that
meillo@114	2298 .Pn mhshow
meillo@114	2299 should display a message in one single pager session.
meillo@114	2300 Therefore,
meillo@114	2301 .Pn mhshow
meillo@114	2302 invokes a pager session for all its output,
meillo@114	2303 whenever it prints to a terminal.
meillo@114	2304 .Ci a4197ea6ffc5c1550e8b52d5a654bcaaaee04a4e
meillo@114	2305 In consequence,
meillo@114	2306 .Pn mhl
meillo@114	2307 does no more invoke a pager.
meillo@114	2308 .Ci 0e46503be3c855bddaeae3843e1b659279c35d70
meillo@114	2309 With
meillo@114	2310 .Pn mhshow
meillo@114	2311 replacing the original
meillo@114	2312 .Pn show ,
meillo@114	2313 output from
meillo@114	2314 .Pn mhl
meillo@114	2315 does not go to the terminal directly, but through
meillo@114	2316 .Pn mhshow .
meillo@114	2317 Hence,
meillo@114	2318 .Pn mhl
meillo@114	2319 does not need to invoke a pager.
meillo@114	2320 The one and only job of
meillo@114	2321 .Pn mhl
meillo@114	2322 is to format messages or parts of them.
meillo@114	2323 The only place in mmh, where a pager is invoked is
meillo@114	2324 .Pn mhshow .
meillo@114	2325 .P
meillo@114	2326 .Pe mhshow-show-*
meillo@114	2327 profile entries can be used to display MIME parts in a specific way.
meillo@114	2328 For instance, PDF and Postscript files could be converted to plain text
meillo@114	2329 to display them in the terminal.
meillo@169	2330 In mmh, MIME parts will always be displayed serially.
meillo@114	2331 The request to display the MIME type `multipart/parallel' in parallel
meillo@114	2332 is ignored.
meillo@114	2333 It is simply treated as `multipart/mixed'.
meillo@114	2334 .Ci d0581ba306a7299113a346f9b4c46ce97bc4cef6
meillo@114	2335 This could already be requested with the, now removed,
meillo@114	2336 .Sw -serialonly
meillo@114	2337 switch of
meillo@114	2338 .Pn mhshow .
meillo@179	2339 As MIME parts are always processed exclusively, i.e. serially,
meillo@114	2340 the `%e' escape in
meillo@114	2341 .Pe mhshow-show-*
meillo@114	2342 profile entries became useless and was thus removed.
meillo@114	2343 .Ci a20d405db09b7ccca74d3e8c57550883da49e1ae
meillo@114	2344 .P
meillo@114	2345 In the intended setup, only text content would be displayed.
meillo@114	2346 Non-text content would be converted to text by appropriate
meillo@114	2347 .Pe mhshow-show-*
meillo@114	2348 profile entries before, if possible and wanted.
meillo@114	2349 All output would be displayed in a single pager session.
meillo@114	2350 Other kinds of attachments are ignored.
meillo@114	2351 With
meillo@114	2352 .Pe mhshow-show-*
meillo@114	2353 profile entries for them, they can be displayed serially along
meillo@114	2354 the message.
meillo@114	2355 For parallel display, the attachments need to be stored to disk first.
meillo@114	2356 .P
meillo@114	2357 To display text content in foreign charsets, they need to be converted
meillo@114	2358 to the native charset.
meillo@114	2359 Therefore,
meillo@114	2360 .Pe mhshow-charset-*
meillo@114	2361 profile entries used to be needed.
meillo@169	2362 In mmh, the conversion is performed automatically by piping the
meillo@169	2363 text through the
meillo@114	2364 .Pn iconv
meillo@114	2365 command, if necessary.
meillo@114	2366 .Ci 2433122c20baccb10b70b49c04c6b0497b5b3b60
meillo@114	2367 Custom
meillo@114	2368 .Pe mhshow-show-*
meillo@114	2369 rules for textual content might need a
meillo@114	2370 .Cl "iconv -f %c %f \|
meillo@114	2371 prefix to have the text converted to the native charset.
meillo@114	2372 .P
meillo@121	2373 Although the conversion of foreign charsets to the native one
meillo@114	2374 has improved, it is not consistent enough.
meillo@114	2375 Further work needs to be done and
meillo@114	2376 the basic concepts in this field need to be re-thought.
meillo@114	2377 Though, the default setup of mmh displays message in foreign charsets
meillo@114	2378 correctly without the need to configure anything.
meillo@114	2379
meillo@114	2380
meillo@114	2381 .ig
meillo@114	2382
meillo@114	2383 .P
meillo@114	2384 mhshow/mhstore: Removed support for retrieving message/external-body parts.
meillo@173	2385 These tools will not download the contents automatically anymore. Instead,
meillo@114	2386 they print the information needed to get the contents. If someone should
meillo@114	2387 really receive one of those rare message/external-body messages, he can
meillo@114	2388 do the job manually. We save nearly a thousand lines of code. That's worth
meillo@114	2389 it!
meillo@114	2390 (The profile entry `nmh-access-ftp' and sbr/ruserpass.c for reading
meillo@114	2391 ~/.netrc are gone now.)
meillo@114	2392 .Ci 55e1d8c654ee0f7c45b9361ce34617983b454c32
meillo@114	2393
meillo@114	2394 ..
meillo@102	2395
meillo@58	2396
meillo@58	2397
meillo@166	2398 .H2 "Signing and Encrypting
meillo@22	2399 .P
meillo@166	2400 Nmh offers no direct support for digital signatures and message encryption.
meillo@157	2401 This functionality needed to be added through third-party software.
meillo@166	2402 In mmh, the functionality should be included because it
meillo@166	2403 is a part of modern email and likely wanted by users of mmh.
meillo@157	2404 A fresh mmh installation should support signing and encrypting
meillo@157	2405 out-of-the-box.
meillo@157	2406 Therefore, Neil Rickert's
meillo@157	2407 .Pn mhsign
meillo@157	2408 and
meillo@157	2409 .Pn mhpgp
meillo@157	2410 scripts
meillo@157	2411 .[
meillo@157	2412 neil rickert mhsign mhpgp
meillo@157	2413 .]
meillo@177	2414 were included into mmh
meillo@177	2415 .Ci f45cdc98117a84f071759462c7ae212f4bc5ab2e
meillo@177	2416 .Ci 58cf09aa36e9f7f352a127158bbf1c5678bc6ed8 .
meillo@177	2417 The scripts fit well because they are lightweight and
meillo@177	2418 similar of style to the existing tools.
meillo@157	2419 Additionally, no licensing difficulties appeared,
meillo@157	2420 as they are part of the public domain.
meillo@112	2421 .P
meillo@157	2422 .Pn mhsign
meillo@157	2423 handles the signing and encrypting part.
meillo@157	2424 It comprises about 250 lines of shell code and interfaces between
meillo@157	2425 .Pn gnupg
meillo@157	2426 and
meillo@157	2427 the MH system.
meillo@177	2428 It was meant to be invoked manually at the WhatNow prompt, but in mmh,
meillo@157	2429 .Pn send
meillo@177	2430 invokes
meillo@177	2431 .pn mhsign
meillo@177	2432 automatically
meillo@177	2433 .Ci c7b5e1df086bcc37ff40163ee67571f076cf6683 .
meillo@177	2434 Special header fields were introduced to request this action.
meillo@157	2435 If a draft contains the
meillo@157	2436 .Hd Sign
meillo@157	2437 header field,
meillo@157	2438 .Pn send
meillo@177	2439 will initiate the signing.
meillo@177	2440 The signing key is either chosen automatically or specified by the
meillo@157	2441 .Pe Pgpkey
meillo@157	2442 profile entry.
meillo@157	2443 .Pn send
meillo@177	2444 always create signatures using the PGP/MIME standard, \" REF XXX
meillo@157	2445 but by manually invoking
meillo@157	2446 .Pn mhsign ,
meillo@157	2447 old-style non-MIME signatures can be created as well.
meillo@177	2448 To encrypt an outgoing message, the draft needs to contain an
meillo@157	2449 .Hd Enc
meillo@157	2450 header field.
meillo@177	2451 Public keys of all recipients are searched for in the gnupg keyring and
meillo@177	2452 in a file called
meillo@177	2453 .Fn pgpkeys ,
meillo@177	2454 which contains exceptions and overrides.
meillo@157	2455 Unless public keys are found for all recipients,
meillo@177	2456 .Pn mhsign
meillo@177	2457 will refuse to encrypt it.
meillo@157	2458 Currently, messages with hidden (BCC) recipients can not be encrypted.
meillo@171	2459 This work is pending because it requires a structurally more complex
meillo@171	2460 approach.
meillo@157	2461 .P
meillo@177	2462 .Pn mhpgp
meillo@177	2463 is the companion to
meillo@177	2464 .Pn mhsign .
meillo@177	2465 It verifies signatures and decrypts messages.
meillo@177	2466 Encrypted messages can either be temporarily decrypted for display
meillo@177	2467 or permanently decrypted and stored into the current folder.
meillo@177	2468 Currently,
meillo@177	2469 .Pn mhpgp
meillo@177	2470 needs to be invoked manually.
meillo@177	2471 The integration into
meillo@177	2472 .Pn show
meillo@177	2473 and
meillo@177	2474 .Pn mhstore
meillo@177	2475 to verify signatures and decrypt messages as needs
meillo@177	2476 is planned but not realized yet.
meillo@177	2477 .P
meillo@177	2478 Both scripts were written for nmh, hence they needed to be adjust
meillo@177	2479 according to the differences between nmh and mmh.
meillo@177	2480 For instance, they use the backup prefix no longer.
meillo@181	2481 Furthermore, compatibility support for old PGP features was dropped.
meillo@177	2482 .P
meillo@157	2483 The integrated message signing and encrypting support is one of the
meillo@157	2484 most recent features in mmh.
meillo@177	2485 It has not yet had the time to mature.
meillo@177	2486 User feedback and personal experience need to be accumulated to
meillo@177	2487 direct the further development of the facility.
meillo@177	2488 Although the feedback and experience is still missing,
meillo@177	2489 it seems to be worthwhile to consider adding
meillo@157	2490 .Sw -[no]sign
meillo@157	2491 and
meillo@157	2492 .Sw -[no]enc
meillo@157	2493 switches to
meillo@157	2494 .Pn send ,
meillo@177	2495 to be able to override the corresponding header fields.
meillo@177	2496 A profile entry:
meillo@157	2497 .VS
meillo@157	2498 send: -sign
meillo@157	2499 VE
meillo@177	2500 would then activate signing for all outgoing messages.
meillo@177	2501 With the present approach, a
meillo@177	2502 .Hd Send
meillo@177	2503 header component needs to be added to each draft template
meillo@177	2504 to achieve the same result.
meillo@177	2505 Adding the switches would ease the work greatly and keep the
meillo@177	2506 template files clean.
meillo@157	2507
meillo@58	2508
meillo@58	2509
meillo@102	2510
meillo@133	2511 .H2 "Draft and Trash Folder
meillo@131	2512 .P
meillo@58	2513
meillo@131	2514 .U3 "Draft Folder
meillo@154	2515 .Id draft-folder
meillo@131	2516 .P
meillo@131	2517 In the beginning, MH had the concept of a draft message.
meillo@131	2518 This is the file
meillo@131	2519 .Fn draft
meillo@131	2520 in the MH directory, which is treated special.
meillo@131	2521 On composing a message, this draft file was used.
meillo@131	2522 When starting to compose another message before the former one was sent,
meillo@131	2523 the user had to decide among:
meillo@171	2524 .LI 1
meillo@168	2525 Using the old draft to finish and send it before starting with a new one.
meillo@171	2526 .LI 2
meillo@168	2527 Discarding the old draft and replacing it with a new one.
meillo@171	2528 .LI 3
meillo@168	2529 Preserving the old draft by refiling it to a folder.
meillo@171	2530 .LP
meillo@168	2531 It was only possible to work in alternation on multiple drafts.
meillo@131	2532 Therefore, the current draft needed to be refiled to a folder and
meillo@168	2533 another one re-used for editing.
meillo@131	2534 Working on multiple drafts at the same time was impossible.
meillo@131	2535 The usual approach of switching to a different MH context did not
meillo@168	2536 help anything.
meillo@131	2537 .P
meillo@131	2538 The draft folder facility exists to
meillo@131	2539 allow true parallel editing of drafts, in a straight forward way.
meillo@131	2540 It was introduced by Marshall T. Rose, already in 1984.
meillo@131	2541 Similar to other new features, the draft folder was inactive by default.
meillo@131	2542 Even in nmh, the highly useful draft folder was not available
meillo@131	2543 out-of-the-box.
meillo@131	2544 At least, Richard Coleman added the man page
meillo@131	2545 .Mp mh-draft (5)
meillo@131	2546 to better document the feature.
meillo@131	2547 .P
meillo@131	2548 Not using the draft folder facility has the single advantage of having
meillo@131	2549 the draft file at a static location.
meillo@131	2550 This is simple in simple cases but the concept does not scale for more
meillo@131	2551 complex cases.
meillo@131	2552 The concept of the draft message is too limited for the problem.
meillo@131	2553 Therefore the draft folder was introduced.
meillo@131	2554 It is the more powerful and more natural concept.
meillo@131	2555 The draft folder is a folder like any other folder in MH.
meillo@131	2556 Its messages can be listed like any other messages.
meillo@131	2557 A draft message is no longer a special case.
meillo@131	2558 Tools do not need special switches to work on the draft message.
meillo@171	2559 Hence corner cases were removed.
meillo@131	2560 .P
meillo@131	2561 The trivial part of the work was activating the draft folder with a
meillo@131	2562 default name.
meillo@131	2563 I chose the name
meillo@131	2564 .Fn +drafts
meillo@131	2565 for obvious reasons.
meillo@131	2566 In consequence, the command line switches
meillo@131	2567 .Sw -draftfolder
meillo@131	2568 and
meillo@131	2569 .Sw -draftmessage
meillo@131	2570 could be removed.
meillo@131	2571 More difficult but also more improving was updating the tools to the
meillo@131	2572 new concept.
meillo@131	2573 For nearly three decades, the tools needed to support two draft handling
meillo@131	2574 approaches.
meillo@131	2575 By fully switching to the draft folder, the tools could be simplified
meillo@131	2576 by dropping the awkward draft message handling code.
meillo@131	2577 .Sw -draft
meillo@131	2578 switches were removed because operating on a draft message is no longer
meillo@131	2579 special.
meillo@131	2580 It became indistinguishable to operating on any other message.
meillo@168	2581 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@168	2582 .P
meillo@168	2583 There is no more need to query the user for draft handling
meillo@168	2584 .Ci 2d48b455c303a807041c35e4248955f8bec59eeb .
meillo@131	2585 It is always possible to add another new draft.
meillo@131	2586 Refiling drafts is without difference to refiling other messages.
meillo@168	2587 All of these special cases are gone.
meillo@131	2588 Yet, one draft-related switch remained.
meillo@131	2589 .Pn comp
meillo@131	2590 still has
meillo@131	2591 .Sw -[no]use
meillo@131	2592 for switching between two modes:
meillo@171	2593 .LI 1
meillo@168	2594 .Sw -use
meillo@168	2595 to modify an existing draft.
meillo@171	2596 .LI 2
meillo@168	2597 .Sw -nouse
meillo@168	2598 to compose a new draft, possibly taking some existing message as template.
meillo@171	2599 .LP
meillo@131	2600 In either case, the behavior of
meillo@131	2601 .Pn comp
meillo@131	2602 is deterministic.
meillo@131	2603 .P
meillo@131	2604 .Pn send
meillo@131	2605 now operates on the current message in the draft folder by default.
meillo@131	2606 As message and folder can both be overridden by specifying them on
meillo@131	2607 the command line, it is possible to send any message in the mail storage
meillo@131	2608 by simply specifying its number and folder.
meillo@131	2609 In contrast to the other tools,
meillo@131	2610 .Pn send
meillo@131	2611 takes the draft folder as its default folder.
meillo@131	2612 .P
meillo@131	2613 Dropping the draft message concept in favor for the draft folder concept,
meillo@131	2614 removed special cases with regular cases.
meillo@131	2615 This simplified the source code of the tools, as well as the concepts.
meillo@131	2616 In mmh, draft management does not break with the MH concepts
meillo@131	2617 but applies them.
meillo@133	2618 .Cl "scan +drafts" ,
meillo@133	2619 for instance, is a truly natural request.
meillo@169	2620 Most of the work was already performed by Rose in the eighties.
meillo@133	2621 The original improvement of mmh is dropping the old draft message approach
meillo@133	2622 and thus simplifying the tools, the documentation and the system as a whole.
meillo@131	2623 Although my part in the draft handling improvement was small,
meillo@133	2624 it was an important one.
meillo@131	2625
meillo@131	2626
meillo@131	2627 .U3 "Trash Folder
meillo@154	2628 .Id trash-folder
meillo@131	2629 .P
meillo@131	2630 Similar to the situation for drafts is the situation for removed messages.
meillo@131	2631 Historically, a message was ``deleted'' by prepending a specific
meillo@173	2632 \fIbackup prefix\fP, usually the comma character,
meillo@173	2633 to the file name.
meillo@164	2634 The specific file would then be ignored by MH because only files with
meillo@164	2635 names consisting of digits only are treated as messages.
meillo@131	2636 Although files remained in the file system,
meillo@168	2637 the messages were no longer visible in MH.
meillo@168	2638 To truly delete them, a maintenance job was needed.
meillo@168	2639 Usually a cron job was installed to delete them after a grace time.
meillo@131	2640 For instance:
meillo@131	2641 .VS
meillo@131	2642 find $HOME/Mail -type f -name ',*' -ctime +7 -delete
meillo@131	2643 VE
meillo@168	2644 In such a setup, the original message could be restored
meillo@131	2645 within the grace time interval by stripping the
meillo@164	2646 backup prefix from the file name.
meillo@168	2647 But the user could not rely on this statement.
meillo@168	2648 If the last message of a folder with six messages (\fL1-6\fP) was removed,
meillo@131	2649 message
meillo@131	2650 .Fn 6 ,
meillo@168	2651 became file
meillo@131	2652 .Fn ,6 .
meillo@168	2653 If then a new message entered the same folder, it would be named with
meillo@168	2654 the number one above the highest existing message number.
meillo@168	2655 In this case the message would be named
meillo@131	2656 .Fn 6
meillo@131	2657 then.
meillo@168	2658 If this new message would be removed as well,
meillo@168	2659 then the backup of the former message is overwritten.
meillo@168	2660 Hence, the ability to restore removed messages did not only depend on
meillo@181	2661 the sweeping cron job but also on the removing of further messages.
meillo@131	2662 It is undesirable to have such obscure and complex mechanisms.
meillo@168	2663 The user should be given a small set of clear assertions, such as
meillo@131	2664 ``Removed files are restorable within a seven-day grace time.''
meillo@131	2665 With the addition ``... unless a message with the same name in the
meillo@131	2666 same folder is removed before.'' the statement becomes complex.
meillo@131	2667 A user will hardly be able to keep track of any removal to know
meillo@131	2668 if the assertion still holds true for a specific file.
meillo@164	2669 In practice, the real mechanism is unclear to the user.
meillo@131	2670 The consequences of further removals are not obvious.
meillo@131	2671 .P
meillo@181	2672 Furthermore, the backup files are scattered within the whole mail storage.
meillo@131	2673 This complicates managing them.
meillo@164	2674 It is possible with the help of
meillo@131	2675 .Pn find ,
meillo@131	2676 but everything would be more convenient
meillo@131	2677 if the deleted messages would be collected in one place.
meillo@131	2678 .P
meillo@131	2679 The profile entry
meillo@131	2680 .Pe rmmproc
meillo@131	2681 (previously named
meillo@131	2682 .Pe Delete-Prog )
meillo@131	2683 was introduced very early to improve the situation.
meillo@164	2684 It could be set to any command, which would be executed to remove
meillo@131	2685 the specified messages.
meillo@168	2686 This would override the default action described above.
meillo@168	2687 Refiling the to-be-removed files to a trash folder is the usual example.
meillo@131	2688 Nmh's man page
meillo@131	2689 .Mp rmm (1)
meillo@131	2690 proposes to set the
meillo@131	2691 .Pe rmmproc
meillo@131	2692 to
meillo@131	2693 .Cl "refile +d
meillo@168	2694 to move messages to the trash folder,
meillo@131	2695 .Fn +d ,
meillo@131	2696 instead of renaming them with the backup prefix.
meillo@131	2697 The man page proposes additionally the expunge command
meillo@131	2698 .Cl "rm `mhpath +d all`
meillo@168	2699 to empty the trash folder.
meillo@131	2700 .P
meillo@131	2701 Removing messages in such a way has advantages.
meillo@131	2702 The mail storage is prevented from being cluttered with removed messages
meillo@131	2703 because they are all collected in one place.
meillo@131	2704 Existing and removed messages are thus separated more strictly.
meillo@131	2705 No backup files are silently overwritten.
meillo@164	2706 But most important is the ability to keep removed messages in the MH domain.
meillo@131	2707 Messages in the trash folder can be listed like those in any other folder.
meillo@131	2708 Deleted messages can be displayed like any other messages.
meillo@169	2709 .Pn refile
meillo@169	2710 can restore deleted messages.
meillo@131	2711 All operations on deleted files are still covered by the MH tools.
meillo@131	2712 The trash folder is just like any other folder in the mail storage.
meillo@131	2713 .P
meillo@131	2714 Similar to the draft folder case, I dropped the old backup prefix approach
meillo@131	2715 in favor for replacing it by the better suiting trash folder system.
meillo@131	2716 Hence,
meillo@131	2717 .Pn rmm
meillo@131	2718 calls
meillo@131	2719 .Pn refile
meillo@131	2720 to move the to-be-removed message to the trash folder,
meillo@131	2721 .Fn +trash
meillo@131	2722 by default.
meillo@164	2723 To sweep it clean, the user can use
meillo@131	2724 .Cl "rmm -unlink +trash a" ,
meillo@131	2725 where the
meillo@131	2726 .Sw -unlink
meillo@131	2727 switch causes the files to be unlinked.
meillo@168	2728 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@168	2729 .Ci ca0b3e830b86700d9e5e31b1784de2bdcaf58fc5
meillo@131	2730 .P
meillo@168	2731 Dropping the legacy approach and converting to the new approach completely
meillo@131	2732 simplified the code base.
meillo@131	2733 The relationship between
meillo@131	2734 .Pn rmm
meillo@131	2735 and
meillo@131	2736 .Pn refile
meillo@131	2737 was inverted.
meillo@131	2738 In mmh,
meillo@131	2739 .Pn rmm
meillo@131	2740 invokes
meillo@131	2741 .Pn refile ,
meillo@131	2742 which used to be the other way round.
meillo@131	2743 Yet, the relationship is simpler now.
meillo@164	2744 Loops, like described in nmh's man page for
meillo@131	2745 .Mp refile (1),
meillo@164	2746 can no longer occur:
meillo@131	2747 .QS
meillo@131	2748 Since
meillo@131	2749 .Pn refile
meillo@131	2750 uses your
meillo@131	2751 .Pe rmmproc
meillo@131	2752 to delete the message, the
meillo@131	2753 .Pe rmmproc
meillo@131	2754 must NOT call
meillo@131	2755 .Pn refile
meillo@131	2756 without specifying
meillo@131	2757 .Sw -normmproc
meillo@131	2758 or you will create an infinite loop.
meillo@131	2759 .QE
meillo@131	2760 .LP
meillo@131	2761 .Pn rmm
meillo@131	2762 either unlinks a message with
meillo@131	2763 .Fu unlink()
meillo@131	2764 or invokes
meillo@131	2765 .Pn refile
meillo@131	2766 to move it to the trash folder.
meillo@131	2767 .Pn refile
meillo@131	2768 does not invoke any tools.
meillo@131	2769 .P
meillo@136	2770 By generalizing the message removal in the way that it became covered
meillo@136	2771 by the MH concepts made the whole system more powerful.
meillo@131	2772
meillo@131	2773
meillo@131	2774
meillo@131	2775
meillo@131	2776
meillo@133	2777 .H2 "Modern Defaults
meillo@133	2778 .P
meillo@133	2779 Nmh has a bunch of convenience-improving features inactive by default,
meillo@133	2780 although one can expect every new user wanting to have them active.
meillo@133	2781 The reason they are inactive by default is the wish to stay compatible
meillo@133	2782 with old versions.
meillo@136	2783 But what is the definition for old versions?
meillo@136	2784 Still, the highly useful draft folder facility has not been activated
meillo@136	2785 by default although it was introduced over twenty-five years ago.
meillo@133	2786 .[
meillo@133	2787 rose romine real work
meillo@133	2788 .]
meillo@136	2789 The community seems not to care.
meillo@136	2790 This is one of several examples that require new users to first build up
meillo@136	2791 a profile before they can access the modern features of nmh.
meillo@136	2792 Without an extensive profile, the setup is hardly usable
meillo@133	2793 for modern emailing.
meillo@133	2794 The point is not the customization of the setup,
meillo@136	2795 but the need to activate generally useful facilities.
meillo@133	2796 .P
meillo@133	2797 Yet, the real problem lies less in enabling the features, as this is
meillo@133	2798 straight forward as soon as one knows what he wants.
meillo@168	2799 The real problem is that new users need deep insight into the project
meillo@168	2800 to find out about inactive features nmh already provides.
meillo@133	2801 To give an example, I needed one year of using nmh
meillo@133	2802 before I became aware of the existence of the attachment system.
meillo@133	2803 One could argue that this fact disqualifies my reading of the
meillo@133	2804 documentation.
meillo@133	2805 If I would have installed nmh from source back then, I could agree.
meillo@133	2806 Yet, I had used a prepackaged version and had expected that it would
meillo@133	2807 just work.
meillo@133	2808 Nevertheless, I had been convinced by the concepts of MH already
meillo@133	2809 and I am a software developer,
meillo@133	2810 still I required a lot of time to discover the cool features.
meillo@133	2811 How can we expect users to be even more advanced than me,
meillo@133	2812 just to allow them use MH in a convenient and modern way?
meillo@133	2813 Unless they are strongly convinced of the concepts, they will fail.
meillo@133	2814 I have seen friends of me giving up disappointed
meillo@133	2815 before they truly used the system,
meillo@133	2816 although they had been motivated in the beginning.
meillo@173	2817 They suffer hard enough to get used to the tool chest approach,
meillo@179	2818 we developers should spare them further inconveniences.
meillo@133	2819 .P
meillo@136	2820 Maintaining compatibility for its own sake is bad,
meillo@136	2821 because the code base collects more and more compatibility code.
meillo@136	2822 Sticking to the compatiblity code means remaining limited;
meillo@168	2823 whereas adjusting to the changes renders the compatibility unnecessary.
meillo@168	2824 Keeping unused alternatives in the code is a bad choice as they likely
meillo@136	2825 gather bugs, by not being well tested.
meillo@136	2826 Also, the increased code size and the greater number of conditions
meillo@136	2827 increase the maintenance costs.
meillo@133	2828 If any MH implementation would be the back-end of widespread
meillo@133	2829 email clients with large user bases, compatibility would be more
meillo@133	2830 important.
meillo@133	2831 Yet, it appears as if this is not the case.
meillo@133	2832 Hence, compatibility is hardly important for technical reasons.
meillo@133	2833 Its importance originates rather from personal reasons.
meillo@133	2834 Nmh's user base is small and old.
meillo@133	2835 Changing the interfaces would cause inconvenience to long-term users of MH.
meillo@133	2836 It would force them to change their many years old MH configurations.
meillo@168	2837 I do understand this aspect, but by sticking to the old users,
meillo@168	2838 new users are kept away.
meillo@133	2839 Yet, the future lies in new users.
meillo@168	2840 In consequence, mmh invites new users by providing a convenient
meillo@168	2841 and modern setup, readily usable out-of-the-box.
meillo@133	2842 .P
meillo@136	2843 In mmh, all modern features are active by default and many previous
meillo@136	2844 approaches are removed or only accessible in manual ways.
meillo@136	2845 New default features include:
meillo@133	2846 .BU
meillo@133	2847 The attachment system (\c
meillo@133	2848 .Hd Attach ).
meillo@133	2849 .Ci 8ff284ff9167eff8f5349481529332d59ed913b1
meillo@133	2850 .BU
meillo@133	2851 The draft folder facility (\c
meillo@133	2852 .Fn +drafts ).
meillo@133	2853 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@133	2854 .BU
meillo@133	2855 The unseen sequence (`u')
meillo@133	2856 .Ci c2360569e1d8d3678e294eb7c1354cb8bf7501c1
meillo@133	2857 and the sequence negation prefix (`!').
meillo@133	2858 .Ci db74c2bd004b2dc9bf8086a6d8bf773ac051f3cc
meillo@133	2859 .BU
meillo@133	2860 Quoting the original message in the reply.
meillo@133	2861 .Ci 67411b1f95d6ec987b4c732459e1ba8a8ac192c6
meillo@133	2862 .BU
meillo@133	2863 Forwarding messages using MIME.
meillo@133	2864 .Ci 6e271608b7b9c23771523f88d23a4d3593010cf1
meillo@171	2865 .LP
meillo@136	2866 In consequence, a setup with a profile that defines only the path to the
meillo@136	2867 mail storage, is already convenient to use.
meillo@168	2868 Again, Paul Vixie's ``edginess'' call supports the direction I took:
meillo@136	2869 ``the `main branch' should just be modern''.
meillo@136	2870 .[
meillo@136	2871 paul vixie edginess nmh-workers
meillo@136	2872 .]
meillo@131	2873
meillo@133	2874
meillo@133	2875
meillo@133	2876
meillo@133	2877
meillo@133	2878 .\" --------------------------------------------------------------
meillo@131	2879 .H1 "Styling
meillo@22	2880 .P
meillo@118	2881 Kernighan and Pike have emphasized the importance of style in the
meillo@118	2882 preface of their book:
meillo@118	2883 .[ [
meillo@118	2884 kernighan pike practice of programming
meillo@118	2885 .], p. x]
meillo@118	2886 .QS
meillo@118	2887 Chapter 1 discusses programming style.
meillo@118	2888 Good style is so important to good programming that we have chose
meillo@118	2889 to cover it first.
meillo@118	2890 .QE
meillo@168	2891 This section covers changes in mmh that were guided by the desire
meillo@118	2892 to improve on style.
meillo@118	2893 Many of them follow the rules given in the quoted book.
meillo@118	2894 .[
meillo@118	2895 kernighan pike practice of programming
meillo@118	2896 .]
meillo@118	2897
meillo@118	2898
meillo@127	2899
meillo@127	2900
meillo@127	2901 .H2 "Code Style
meillo@154	2902 .Id code-style
meillo@118	2903 .P
meillo@118	2904 .U3 "Indentation Style
meillo@118	2905 .P
meillo@118	2906 Indentation styles are the holy cow of programmers.
meillo@168	2907 Kernighan and Pike
meillo@118	2908 .[ [
meillo@118	2909 kernighan pike practice of programming
meillo@118	2910 .], p. 10]
meillo@168	2911 wrote:
meillo@118	2912 .QS
meillo@118	2913 Programmers have always argued about the layout of programs,
meillo@118	2914 but the specific style is much less important than its consistent
meillo@118	2915 application.
meillo@121	2916 Pick one style, preferably ours, use it consistently, and don't waste
meillo@118	2917 time arguing.
meillo@118	2918 .QE
meillo@118	2919 .P
meillo@118	2920 I agree that the constant application is most important,
meillo@118	2921 but I believe that some styles have advantages over others.
meillo@118	2922 For instance the indentation with tab characters only.
meillo@118	2923 Tab characters directly map to the nesting level \(en
meillo@118	2924 one tab, one level.
meillo@118	2925 Tab characters are flexible because developers can adjust them to
meillo@118	2926 whatever width they like to have.
meillo@118	2927 There is no more need to run
meillo@118	2928 .Pn unexpand
meillo@118	2929 or
meillo@118	2930 .Pn entab
meillo@118	2931 programs to ensure the correct mixture of leading tabs and spaces.
meillo@118	2932 The simple rules are: (1) Leading whitespace must consist of tabs only.
meillo@118	2933 (2) Any other whitespace should consist of spaces.
meillo@121	2934 These two rules ensure the integrity of the visual appearance.
meillo@121	2935 Although reformatting existing code should be avoided, I did it.
meillo@136	2936 I did not waste time arguing; I just reformated the code.
meillo@118	2937 .Ci a485ed478abbd599d8c9aab48934e7a26733ecb1
meillo@118	2938
meillo@118	2939 .U3 "Comments
meillo@118	2940 .P
meillo@118	2941 Section 1.6 of
meillo@118	2942 .[ [
meillo@118	2943 kernighan pike practice of programming
meillo@118	2944 .], p. 23]
meillo@118	2945 demands: ``Don't belabor the obvious.''
meillo@122	2946 Hence, I simply removed all the comments in the following code excerpt:
meillo@118	2947 .VS
meillo@120	2948 context_replace(curfolder, folder); /* update current folder */
meillo@120	2949 seq_setcur(mp, mp->lowsel); /* update current message */
meillo@120	2950 seq_save(mp); /* synchronize message sequences */
meillo@120	2951 folder_free(mp); /* free folder/message structure */
meillo@120	2952 context_save(); /* save the context file */
meillo@120	2953
meillo@120	2954 [...]
meillo@120	2955
meillo@120	2956 int c; /* current character */
meillo@120	2957 char cp; / miscellaneous character pointer */
meillo@120	2958
meillo@120	2959 [...]
meillo@120	2960
meillo@120	2961 /* NUL-terminate the field */
meillo@120	2962 *cp = '\0';
meillo@118	2963 VE
meillo@120	2964 .Ci 426543622b377fc5d091455cba685e114b6df674
meillo@118	2965 .P
meillo@136	2966 The program code explains enough itself, already.
meillo@136	2967
meillo@118	2968
meillo@118	2969 .U3 "Names
meillo@118	2970 .P
meillo@118	2971 Kernighan and Pike suggest:
meillo@118	2972 ``Use active names for functions''.
meillo@118	2973 .[ [
meillo@118	2974 kernighan pike practice of programming
meillo@118	2975 .], p. 4]
meillo@118	2976 One application of this rule was the rename of
meillo@118	2977 .Fu check_charset()
meillo@118	2978 to
meillo@118	2979 .Fu is_native_charset() .
meillo@118	2980 .Ci 8d77b48284c58c135a6b2787e721597346ab056d
meillo@181	2981 The same change fixed a violation of ``Be accurate''
meillo@181	2982 .[ [
meillo@181	2983 kernighan pike practice of programming
meillo@181	2984 .], p. 4]
meillo@181	2985 as well.
meillo@118	2986 The code did not match the expectation the function suggested,
meillo@118	2987 as it, for whatever reason, only compared the first ten characters
meillo@118	2988 of the charset name.
meillo@118	2989 .P
meillo@118	2990 More important than using active names is using descriptive names.
meillo@145	2991 .VS
meillo@145	2992 m_unknown(in); /* the MAGIC invocation... */
meillo@145	2993 VE
meillo@145	2994 Renaming the obscure
meillo@118	2995 .Fu m_unknown()
meillo@145	2996 function was a delightful event, although it made the code less funny.
meillo@118	2997 .Ci 611d68d19204d7cbf5bd585391249cb5bafca846
meillo@118	2998 .P
meillo@118	2999 Magic numbers are generally considered bad style.
meillo@118	3000 Obviously, Kernighan and Pike agree:
meillo@118	3001 ``Give names to magic numbers''.
meillo@118	3002 .[ [
meillo@118	3003 kernighan pike practice of programming
meillo@118	3004 .], p. 19]
meillo@118	3005 One such change was naming the type of input \(en mbox or mail folder \(en
meillo@118	3006 to be scanned:
meillo@118	3007 .VS
meillo@118	3008 #define SCN_MBOX (-1)
meillo@118	3009 #define SCN_FOLD 0
meillo@118	3010 VE
meillo@118	3011 .Ci 7ffb36d28e517a6f3a10272056fc127592ab1c19
meillo@118	3012 .P
meillo@118	3013 The argument
meillo@118	3014 .Ar outnum
meillo@118	3015 of the function
meillo@118	3016 .Fu scan()
meillo@118	3017 in
meillo@118	3018 .Fn uip/scansbr.c
meillo@118	3019 defines the number of the message to be created.
meillo@118	3020 If no message is to be created, the argument is misused to transport
meillo@118	3021 program logic.
meillo@118	3022 This lead to obscure code.
meillo@118	3023 I improved the clarity of the code by introducing two variables:
meillo@118	3024 .VS
meillo@118	3025 int incing = (outnum > 0);
meillo@118	3026 int ismbox = (outnum != 0);
meillo@118	3027 VE
meillo@118	3028 They cover the magic values and are used for conditions.
meillo@118	3029 The variable
meillo@118	3030 .Ar outnum
meillo@118	3031 is only used when it holds an ordinary message number.
meillo@118	3032 .Ci b8b075c77be7794f3ae9ff0e8cedb12b48fd139f
meillo@118	3033 The clarity improvement of the change showed detours in the program logic
meillo@118	3034 of related code parts.
meillo@118	3035 Having the new variables with descriptive names, a more
meillo@121	3036 straight forward implementation became apparent.
meillo@169	3037 Before the code was clarified, the possibility to improve had not be seen.
meillo@118	3038 .Ci aa60b0ab5e804f8befa890c0a6df0e3143ce0723
meillo@118	3039
meillo@133	3040
meillo@133	3041
meillo@133	3042 .H2 "Structural Rework
meillo@133	3043 .P
meillo@136	3044 Although the stylistic changes described up to here improve the
meillo@136	3045 readability of the source code, all of them are changes ``in the small''.
meillo@136	3046 Structural changes affect a much larger area.
meillo@136	3047 They are more difficult to do but lead to larger improvements,
meillo@136	3048 especially as they influence the outer shape of the tools as well.
meillo@118	3049 .P
meillo@118	3050 At the end of their chapter on style,
meillo@118	3051 Kernighan and Pike ask: ``But why worry about style?''
meillo@181	3052 .[ [
meillo@181	3053 kernighan pike practice of programming
meillo@181	3054 .], p. 28]
meillo@136	3055 Following are two examples of structural rework that show
meillo@136	3056 why style is important in the first place.
meillo@136	3057
meillo@136	3058
meillo@136	3059 .U3 "Rework of \f(CWanno\fP
meillo@118	3060 .P
meillo@120	3061 Until 2002,
meillo@120	3062 .Pn anno
meillo@120	3063 had six functional command line switches,
meillo@120	3064 .Sw -component
meillo@120	3065 and
meillo@120	3066 .Sw -text ,
meillo@168	3067 which have an argument each,
meillo@120	3068 and the two pairs of flags,
meillo@120	3069 .Sw -[no]date
meillo@120	3070 and
meillo@120	3071 .Sw -[no]inplace .
meillo@120	3072 Then Jon Steinhart introduced his attachment system.
meillo@120	3073 In need for more advanced annotation handling, he extended
meillo@120	3074 .Pn anno .
meillo@120	3075 He added five more switches:
meillo@120	3076 .Sw -draft ,
meillo@120	3077 .Sw -list ,
meillo@120	3078 .Sw -delete ,
meillo@120	3079 .Sw -append ,
meillo@120	3080 and
meillo@120	3081 .Sw -number ,
meillo@120	3082 the last one taking an argument.
meillo@121	3083 .Ci 7480dbc14bc90f2d872d434205c0784704213252
meillo@120	3084 Later,
meillo@120	3085 .Sw -[no]preserve
meillo@120	3086 was added.
meillo@121	3087 .Ci d9b1d57351d104d7ec1a5621f090657dcce8cb7f
meillo@120	3088 Then, the Synopsis section of the man page
meillo@120	3089 .Mp anno (1)
meillo@120	3090 read:
meillo@120	3091 .VS
meillo@120	3092 anno [+folder] [msgs] [-component field] [-inplace \| -noinplace]
meillo@120	3093 [-date \| -nodate] [-draft] [-append] [-list] [-delete]
meillo@120	3094 [-number [num\|all]] [-preserve \| -nopreserve] [-version]
meillo@120	3095 [-help] [-text body]
meillo@120	3096 VE
meillo@120	3097 .LP
meillo@120	3098 The implementation followed the same structure.
meillo@120	3099 Problems became visible when
meillo@120	3100 .Cl "anno -list -number 42
meillo@120	3101 worked on the current message instead on message number 42,
meillo@120	3102 and
meillo@120	3103 .Cl "anno -list -number l:5
meillo@124	3104 did not work on the last five messages but failed with the mysterious
meillo@120	3105 error message: ``anno: missing argument to -list''.
meillo@121	3106 Yet, the invocation matched the specification in the man page.
meillo@120	3107 There, the correct use of
meillo@120	3108 .Sw -number
meillo@120	3109 was defined as being
meillo@120	3110 .Cl "[-number [num\|all]]
meillo@120	3111 and the textual description for the combination with
meillo@120	3112 .Sw -list
meillo@120	3113 read:
meillo@120	3114 .QS
meillo@164	3115 The
meillo@164	3116 .Sw -list
meillo@164	3117 option produces a listing of the field bodies for
meillo@120	3118 header fields with names matching the specified component,
meillo@164	3119 one per line. The listing is numbered, starting at 1, if the
meillo@164	3120 .Sw -number
meillo@164	3121 option is also used.
meillo@120	3122 .QE
meillo@120	3123 .LP
meillo@120	3124 The problem was manifold.
meillo@120	3125 The code required a numeric argument to the
meillo@120	3126 .Sw -number
meillo@120	3127 switch.
meillo@120	3128 If it was missing or non-numeric,
meillo@120	3129 .Pn anno
meillo@120	3130 aborted with an error message that had an off-by-one error,
meillo@120	3131 printing the switch one before the failing one.
meillo@120	3132 Semantically, the argument to the
meillo@120	3133 .Sw -number
meillo@120	3134 switch is only necessary in combination with
meillo@120	3135 .Sw -delete ,
meillo@120	3136 but not with
meillo@120	3137 .Sw -list .
meillo@120	3138 .P
meillo@171	3139 Trying to fix these problems on the surface would not have solved
meillo@180	3140 them truly, as they originate from a discrepance between the
meillo@120	3141 structure of the problem and the structure implemented in the program.
meillo@120	3142 Such structural differences can not be cured on the surface.
meillo@120	3143 They need to be solved by adjusting the structure of the implementation
meillo@120	3144 to the structure of the problem.
meillo@120	3145 .P
meillo@120	3146 In 2002, the new switches
meillo@120	3147 .Sw -list
meillo@120	3148 and
meillo@120	3149 .Sw -delete
meillo@120	3150 were added in the same way, the
meillo@120	3151 .Sw -number
meillo@120	3152 switch for instance had been added.
meillo@120	3153 Yet, they are of structural different type.
meillo@120	3154 Semantically,
meillo@120	3155 .Sw -list
meillo@120	3156 and
meillo@120	3157 .Sw -delete
meillo@120	3158 introduce modes of operation.
meillo@120	3159 Historically,
meillo@120	3160 .Pn anno
meillo@120	3161 had only one operation mode: adding header fields.
meillo@180	3162 With the extension it got two more modes:
meillo@180	3163 .\" XXX got
meillo@120	3164 listing and deleting header fields.
meillo@120	3165 The structure of the code changes did not pay respect to this
meillo@120	3166 fundamental change to
meillo@120	3167 .Pn anno 's
meillo@120	3168 behavior.
meillo@120	3169 Neither the implementation nor the documentation did clearly
meillo@120	3170 define them as being exclusive modes of operation.
meillo@120	3171 Having identified the problem, I solved it by putting structure into
meillo@120	3172 .Pn anno
meillo@120	3173 and its documentation.
meillo@120	3174 .Ci d54c8db8bdf01e8381890f7729bc0ef4a055ea11
meillo@120	3175 .P
meillo@173	3176 The difference is visible in both the code and the documentation.
meillo@121	3177 The following code excerpt:
meillo@120	3178 .VS
meillo@120	3179 int delete = -2; /* delete header element if set */
meillo@120	3180 int list = 0; /* list header elements if set */
meillo@120	3181 [...]
meillo@121	3182 case DELETESW: /* delete annotations */
meillo@121	3183 delete = 0;
meillo@121	3184 continue;
meillo@121	3185 case LISTSW: /* produce a listing */
meillo@121	3186 list = 1;
meillo@121	3187 continue;
meillo@120	3188 VE
meillo@121	3189 .LP
meillo@121	3190 was replaced by:
meillo@120	3191 .VS
meillo@120	3192 static enum { MODE_ADD, MODE_DEL, MODE_LIST } mode = MODE_ADD;
meillo@120	3193 [...]
meillo@121	3194 case DELETESW: /* delete annotations */
meillo@121	3195 mode = MODE_DEL;
meillo@121	3196 continue;
meillo@121	3197 case LISTSW: /* produce a listing */
meillo@121	3198 mode = MODE_LIST;
meillo@121	3199 continue;
meillo@120	3200 VE
meillo@120	3201 .LP
meillo@121	3202 The replacement code does not only reflect the problem's structure better,
meillo@121	3203 it is easier to understand as well.
meillo@121	3204 The same applies to the documentation.
meillo@120	3205 The man page was completely reorganized to propagate the same structure.
meillo@121	3206 This is visible in the Synopsis section:
meillo@120	3207 .VS
meillo@120	3208 anno [+folder] [msgs] [-component field] [-text body]
meillo@120	3209 [-append] [-date \| -nodate] [-preserve \| -nopreserve]
meillo@120	3210 [-Version] [-help]
meillo@120	3211
meillo@120	3212 anno -delete [+folder] [msgs] [-component field] [-text
meillo@120	3213 body] [-number num \| all ] [-preserve \| -nopreserve]
meillo@120	3214 [-Version] [-help]
meillo@120	3215
meillo@120	3216 anno -list [+folder] [msgs] [-component field] [-number]
meillo@120	3217 [-Version] [-help]
meillo@120	3218 VE
meillo@121	3219 .\" XXX think about explaining the -preserve rework?
meillo@118	3220
meillo@58	3221
meillo@58	3222
meillo@133	3223 .U3 "Path Conversion
meillo@133	3224 .P
meillo@134	3225 Four kinds of path names can appear in MH:
meillo@171	3226 .LI 1
meillo@134	3227 Absolute Unix directory paths, like
meillo@134	3228 .Fn /etc/passwd .
meillo@171	3229 .LI 2
meillo@134	3230 Relative Unix directory paths, like
meillo@134	3231 .Fn ./foo/bar .
meillo@171	3232 .LI 3
meillo@134	3233 Absolute MH folder paths, like
meillo@134	3234 .Fn +friends/phil .
meillo@171	3235 .LI 4
meillo@134	3236 Relative MH folder paths, like
meillo@134	3237 .Fn @subfolder .
meillo@171	3238 .LP
meillo@134	3239 The last type, relative MH folder paths, are hardly documented.
meillo@134	3240 Nonetheless, they are useful for large mail storages.
meillo@134	3241 The current mail folder is specified as `\c
meillo@134	3242 .Fn @ ',
meillo@134	3243 just like the current directory is specified as `\c
meillo@134	3244 .Fn . '.
meillo@134	3245 .P
meillo@134	3246 To allow MH tools to understand all four notations,
meillo@134	3247 they need to convert between them.
meillo@180	3248 .\" XXX between?
meillo@134	3249 In nmh, these path name conversion functions were located in the files
meillo@134	3250 .Fn sbr/path.c
meillo@134	3251 (``return a pathname'') and
meillo@134	3252 .Fn sbr/m_maildir.c
meillo@134	3253 (``get the path for the mail directory'').
meillo@134	3254 The seven functions in the two files were documented with no more
meillo@134	3255 than two comments, which described obvious information.
meillo@134	3256 The function signatures were neither explaining:
meillo@134	3257 .VS
meillo@134	3258 char path(char , int);
meillo@134	3259 char pluspath(char );
meillo@134	3260 char m_mailpath(char );
meillo@134	3261 char m_maildir(char );
meillo@134	3262 VE
meillo@134	3263 .P
meillo@134	3264 My investigation provides the following description:
meillo@171	3265 .LI 1
meillo@134	3266 The second parameter of
meillo@134	3267 .Fu path()
meillo@134	3268 defines the type of path given as first parameter.
meillo@134	3269 Directory paths are converted to absolute directory paths.
meillo@134	3270 Folder paths are converted to absolute folder paths.
meillo@173	3271 Folder paths must not include a leading `\fL@\fP' character.
meillo@134	3272 Leading plus characters are preserved.
meillo@134	3273 The result is a pointer to newly allocated memory.
meillo@171	3274 .LI 2
meillo@134	3275 .Fu pluspath()
meillo@134	3276 is a convenience-wrapper to
meillo@134	3277 .Fu path() ,
meillo@134	3278 to convert folder paths only.
meillo@134	3279 This function can not be used for directory paths.
meillo@134	3280 An empty string parameter causes a buffer overflow.
meillo@171	3281 .LI 3
meillo@134	3282 .Fu m_mailpath()
meillo@134	3283 converts directory paths to absolute directory paths.
meillo@173	3284 The characters `\fL+\fP' or `\fL@\fP' at the beginning of the path name are
meillo@134	3285 treated literal, i.e. as the first character of a relative directory path.
meillo@134	3286 Hence, this function can not be used for folder paths.
meillo@134	3287 In any case, the result is an absolute directory path.
meillo@134	3288 The result is a pointer to newly allocated memory.
meillo@171	3289 .LI 4
meillo@134	3290 .Fu m_maildir()
meillo@134	3291 returns the parameter unchanged if it is an absolute directory path
meillo@173	3292 or begins with the entry `\fL.\fP' or `\fL..\fP'.
meillo@134	3293 All other strings are prepended with the current working directory.
meillo@134	3294 Hence, this functions can not be used for folder paths.
meillo@134	3295 The result is either an absolute directory path or a relative
meillo@134	3296 directory path, starting with a dot.
meillo@134	3297 In contrast to the other functions, the result is a pointer to
meillo@134	3298 static memory.
meillo@134	3299 .P
meillo@134	3300 The situation was obscure, irritating, error-prone, and non-orthogonal.
meillo@134	3301 No clear terminology was used to name the different kinds of path names.
meillo@134	3302 The first argument of
meillo@134	3303 .Fu m_mailpath() ,
meillo@134	3304 for instance, was named
meillo@134	3305 .Ar folder ,
meillo@134	3306 though
meillo@134	3307 .Fu m_mailpath()
meillo@134	3308 can not be used for MH folders.
meillo@134	3309 .P
meillo@134	3310 I reworked the path name conversion completely, introducing clarity.
meillo@134	3311 First of all, the terminology needed to be defined.
meillo@134	3312 A path name is either in the Unix domain, then it is called
meillo@134	3313 \fIdirectory path\fP, `dirpath' for short, or it is in the MH domain,
meillo@134	3314 then it is called \fIfolder path\fP, `folpath' for short.
meillo@134	3315 The two terms need to be used with strict distinction.
meillo@134	3316 Having a clear terminology is often an indicator of having understood
meillo@134	3317 the problem itself.
meillo@134	3318 Second, I exploited the concept of path type indicators.
meillo@134	3319 By requesting every path name to start with a clear type identifier,
meillo@134	3320 conversion between the types can be fully automated.
meillo@134	3321 Thus the tools can accept paths of any type from the user.
meillo@134	3322 Therefore, it was necessary to require relative directory paths to be
meillo@134	3323 prefixed with a dot character.
meillo@134	3324 In consequence, the dot character could no longer be an alias for the
meillo@134	3325 current message.
meillo@134	3326 .Ci cff0e16925e7edbd25b8b9d6d4fbdf03e0e60c01
meillo@134	3327 Third, I created three new functions to replace the previous mess:
meillo@171	3328 .LI 1
meillo@134	3329 .Fu expandfol()
meillo@134	3330 converts folder paths to absolute folder paths,
meillo@134	3331 without the leading plus character.
meillo@134	3332 Directory paths are simply passed through.
meillo@134	3333 This function is to be used for folder paths only, thus the name.
meillo@134	3334 The result is a pointer to static memory.
meillo@171	3335 .LI 2
meillo@134	3336 .Fu expanddir()
meillo@134	3337 converts directory paths to absolute directory paths.
meillo@134	3338 Folder paths are treated as relative directory paths.
meillo@134	3339 This function is to be used for directory paths only, thus the name.
meillo@134	3340 The result is a pointer to static memory.
meillo@171	3341 .LI 3
meillo@134	3342 .Fu toabsdir()
meillo@134	3343 converts any type of path to an absolute directory path.
meillo@134	3344 This is the function of choice for path conversion.
meillo@134	3345 Absolute directory paths are the most general representation of a
meillo@134	3346 path name.
meillo@134	3347 The result is a pointer to static memory.
meillo@134	3348 .P
meillo@180	3349 .\" XXX ueberfluessig?
meillo@134	3350 The new functions have names that indicate their use.
meillo@134	3351 Two of the functions convert relative to absolute path names of the
meillo@134	3352 same type.
meillo@134	3353 The third function converts any path name type to the most general one,
meillo@134	3354 the absolute directory path.
meillo@134	3355 All of the functions return pointers to static memory.
meillo@134	3356 All three functions are implemented in
meillo@134	3357 .Fn sbr/path.c .
meillo@134	3358 .Fn sbr/m_maildir.c
meillo@134	3359 is removed.
meillo@168	3360 .Ci d39e2c447b0d163a5a63f480b23d06edb7a73aa0
meillo@134	3361 .P
meillo@134	3362 Along with the path conversion rework, I also replaced
meillo@134	3363 .Fu getfolder(FDEF)
meillo@134	3364 with
meillo@134	3365 .Fu getdeffol()
meillo@134	3366 and
meillo@134	3367 .Fu getfolder(FCUR)
meillo@134	3368 with
meillo@134	3369 .Fu getcurfol() ,
meillo@134	3370 which is only a convenience wrapper for
meillo@134	3371 .Fu expandfol("@") .
meillo@134	3372 This code was moved from
meillo@134	3373 .Fn sbr/getfolder.c
meillo@134	3374 to
meillo@134	3375 .Fn sbr/path.c .
meillo@168	3376 .Ci d39e2c447b0d163a5a63f480b23d06edb7a73aa0
meillo@134	3377 .P
meillo@134	3378 The related function
meillo@134	3379 .Fu etcpath()
meillo@134	3380 was moved to
meillo@134	3381 .Fn sbr/path.c ,
meillo@168	3382 too
meillo@168	3383 .Ci b4c29794c12099556151d93a860ee51badae2e35 .
meillo@134	3384 Previously, it had been located in
meillo@134	3385 .Fn config/config.c ,
meillo@134	3386 for whatever reasons.
meillo@134	3387 .P
meillo@134	3388 .Fn sbr/path.c
meillo@134	3389 now contains all path handling code.
meillo@180	3390 .\" XXX naechste zeile weg?
meillo@134	3391 Only 173 lines of code were needed to replace the previous 252 lines.
meillo@134	3392 The readability of the code is highly improved.
meillo@134	3393 Additionally, each of the six exported and one static functions
meillo@134	3394 is introduced by an explaining comment.
meillo@133	3395
meillo@133	3396
meillo@133	3397
meillo@133	3398
meillo@133	3399 .H2 "Profile Reading
meillo@133	3400 .P
meillo@138	3401 The MH profile contains the configuration for the user-specific MH setup.
meillo@138	3402 MH tools read the profile right after starting up,
meillo@138	3403 as it contains the location of the user's mail storage
meillo@138	3404 and similar settings that influence the whole setup.
meillo@181	3405 Furthermore, the profile contains the default switches for the tools,
meillo@138	3406 hence, it must be read before the command line switches are processed.
meillo@138	3407 .P
meillo@138	3408 For historic reasons, some MH tools did not read the profile and context.
meillo@138	3409 Among them were
meillo@138	3410 .Pn post /\c
meillo@138	3411 .Pn spost ,
meillo@138	3412 .Pn mhmail ,
meillo@138	3413 and
meillo@138	3414 .Pn slocal .
meillo@138	3415 The reason why these tools ignored the profile were not clearly stated.
meillo@138	3416 During the discussion on the nmh-workers mailing list,
meillo@181	3417 David Levine posted an explanation, quoting John Romine:
meillo@138	3418 .[
meillo@138	3419 nmh-workers levine post profile
meillo@138	3420 .]
meillo@138	3421 .QS
meillo@138	3422 I asked John Romine and here's what he had to say, which
meillo@138	3423 agrees and provides an example that convinces me:
meillo@138	3424 .QS
meillo@164	3425 My take on this is that
meillo@164	3426 .Pn post
meillo@164	3427 should not be called by users directly, and it doesn't read the
meillo@164	3428 .Fn .mh_profile
meillo@138	3429 (only front-end UI programs read the profile).
meillo@138	3430 .QP
meillo@164	3431 For example, there can be contexts where
meillo@164	3432 .Pn post
meillo@164	3433 is called by a helper program (like `\c
meillo@164	3434 .Pn mhmail ')
meillo@164	3435 which may be run by a non-MH user.
meillo@164	3436 We don't want this to prompt the user to create an MH profile, etc.
meillo@138	3437 .QP
meillo@164	3438 My suggestion would be to have
meillo@164	3439 .Pn send
meillo@164	3440 pass a (hidden) `\c
meillo@164	3441 .Sw -fileproc
meillo@164	3442 .Ar proc '
meillo@164	3443 option to
meillo@164	3444 .Pn post
meillo@164	3445 if needed.
meillo@164	3446 You could also
meillo@164	3447 use an environment variable (I think
meillo@164	3448 .Pn send /\c
meillo@164	3449 .Pn whatnow
meillo@164	3450 do this).
meillo@138	3451 .QE
meillo@164	3452 I think that's the way to go.
meillo@164	3453 My personal preference is to use a command line option,
meillo@164	3454 not an environment variable.
meillo@138	3455 .QE
meillo@138	3456 .P
meillo@138	3457 To solve the problem of
meillo@138	3458 .Pn post
meillo@138	3459 not honoring the
meillo@138	3460 .Pe fileproc
meillo@138	3461 profile entry,
meillo@138	3462 the community roughly agreed that a switch
meillo@138	3463 .Sw -fileproc
meillo@138	3464 should be added to
meillo@138	3465 .Pn post
meillo@138	3466 to be able to pass a different fileproc.
meillo@138	3467 I strongly disagree with this approach because it does not solve
meillo@138	3468 the problem; it only removes a single symptom.
meillo@138	3469 The problem is that
meillo@138	3470 .Pn post
meillo@138	3471 does not behave as expected.
meillo@138	3472 But all programs should behave as expected.
meillo@138	3473 Clear and simple concepts are a precondition for this.
meillo@138	3474 Hence, the real solution is having all MH tools read the profile.
meillo@138	3475 .P
meillo@180	3476 The problem has a further aspect.
meillo@138	3477 It mainly originates in
meillo@138	3478 .Pn mhmail .
meillo@138	3479 .Pn mhmail
meillo@138	3480 was intended to be a replacement for
meillo@138	3481 .Pn mailx
meillo@138	3482 on systems with MH installations.
meillo@138	3483 .Pn mhmail
meillo@138	3484 should have been able to use just like
meillo@138	3485 .Pn mailx ,
meillo@138	3486 but sending the message via MH's
meillo@138	3487 .Pn post
meillo@138	3488 instead of
meillo@138	3489 .Pn sendmail .
meillo@138	3490 Using
meillo@138	3491 .Pn mhmail
meillo@138	3492 should not be influenced by the question whether the user had
meillo@138	3493 MH set up for himself or not.
meillo@138	3494 .Pn mhmail
meillo@138	3495 did not read the profile as this requests the user to set up MH
meillo@138	3496 if not done yet.
meillo@138	3497 As
meillo@138	3498 .Pn mhmail
meillo@138	3499 used
meillo@138	3500 .Pn post ,
meillo@138	3501 .Pn post
meillo@138	3502 could not read the profile neither.
meillo@138	3503 This is the reason why
meillo@138	3504 .Pn post
meillo@138	3505 does not read the profile.
meillo@138	3506 This is the reason for the actual problem.
meillo@138	3507 It was not much of a problem because
meillo@138	3508 .Pn post
meillo@138	3509 was not intended to be used by users directly.
meillo@138	3510 .Pn send
meillo@138	3511 is the interactive front-end to
meillo@138	3512 .Pn post .
meillo@138	3513 .Pn send
meillo@138	3514 read the profile and passed all relevant values on the command line to
meillo@138	3515 .Pn post
meillo@138	3516 \(en an awkward solution.
meillo@138	3517 .P
meillo@138	3518 The important insight is that
meillo@138	3519 .Pn mhmail
meillo@138	3520 is no true MH tool.
meillo@138	3521 The concepts broke because this outlandish tool was treated as any other
meillo@138	3522 MH tool.
meillo@138	3523 Instead it should have been treated accordingly to its foreign style.
meillo@138	3524 The solution is not to prevent the tools reading the profile but
meillo@138	3525 to instruct them reading a different profile.
meillo@138	3526 .Pn mhmail
meillo@138	3527 could have set up a well-defined profile and caused all MH tools
meillo@180	3528 in the session to use it by exporting an environment variable.
meillo@138	3529 With this approach, no special cases would have been introduced,
meillo@138	3530 no surprises would have been caused.
meillo@138	3531 By writing a clean-profile-wrapper, the concept could have been
meillo@173	3532 generalized orthogonally to the whole MH tool chest.
meillo@138	3533 Then Rose's motivation behind the decision that
meillo@138	3534 .Pn post
meillo@138	3535 ignores the profile, as quoted by Jeffrey Honig,
meillo@181	3536 would have become possible:
meillo@138	3537 .[
meillo@197	3538 nmh-workers honig post profile
meillo@138	3539 .]
meillo@138	3540 .QS
meillo@138	3541 when you run mh commands in a script, you want all the defaults to be
meillo@138	3542 what the man page says.
meillo@138	3543 when you run a command by hand, then you want your own defaults...
meillo@138	3544 .QE
meillo@138	3545 .LP
meillo@171	3546 Yet, I consider this explanation shortsighted.
meillo@138	3547 We should rather regard theses two cases as just two different MH setups,
meillo@138	3548 based on two different profiles.
meillo@138	3549 Mapping such problems on the concepts of switching between different
meillo@138	3550 profiles, solves them once for all.
meillo@138	3551 .P
meillo@138	3552 In mmh, the wish to have
meillo@138	3553 .Pn mhmail
meillo@173	3554 as a replacement for
meillo@138	3555 .Pn mailx
meillo@138	3556 is considered obsolete.
meillo@138	3557 Mmh's
meillo@138	3558 .Pn mhmail
meillo@138	3559 does no longer cover this use-case.
meillo@138	3560 Currently,
meillo@138	3561 .Pn mhmail
meillo@138	3562 is in a transition state.
meillo@138	3563 .Ci 32d4f9daaa70519be3072479232ff7be0500d009
meillo@138	3564 It may become a front-end to
meillo@138	3565 .Pn comp ,
meillo@138	3566 which provides an interface more convenient in some cases.
meillo@138	3567 In this case,
meillo@138	3568 .Pn mhmail
meillo@138	3569 will become an ordinary MH tool, reading the profile.
meillo@138	3570 If, however, this idea will not convince, then
meillo@138	3571 .Pn mhmail
meillo@138	3572 will be removed.
meillo@138	3573 .P
meillo@173	3574 Every program in the mmh tool chest reads the profile.
meillo@138	3575 The only exception is
meillo@138	3576 .Pn slocal ,
meillo@173	3577 which is not considered part of the mmh tool chest.
meillo@138	3578 This MDA is only distributed with mmh, currently.
meillo@138	3579 Mmh has no
meillo@138	3580 .Pn post
meillo@138	3581 program, but
meillo@138	3582 .Pn spost ,
meillo@138	3583 which now reads the profile.
meillo@138	3584 .Ci 3e017a7abbdf69bf0dff7a4073275961eda1ded8
meillo@138	3585 With this change,
meillo@138	3586 .Pn send
meillo@138	3587 and
meillo@138	3588 .Pn spost
meillo@138	3589 can be considered to be merged.
meillo@138	3590 .Pn spost
meillo@169	3591 is only invoked directly by the to-be-changed
meillo@138	3592 .Pn mhmail
meillo@138	3593 implementation and by
meillo@138	3594 .Pn rcvdist ,
meillo@138	3595 which will require rework.
meillo@138	3596 .P
meillo@138	3597 The
meillo@138	3598 .Fu context_foil()
meillo@138	3599 function to pretend to have read an empty profile was removed.
meillo@138	3600 .Ci 68af8da96bea87a5541988870130b6209ce396f6
meillo@138	3601 All mmh tools read the profile.
meillo@133	3602
meillo@133	3603
meillo@127	3604
meillo@121	3605 .H2 "Standard Libraries
meillo@22	3606 .P
meillo@121	3607 MH is one decade older than the POSIX and ANSI C standards.
meillo@121	3608 Hence, MH included own implementations of functions
meillo@121	3609 that are standardized and thus widely available today,
meillo@121	3610 but were not back then.
meillo@121	3611 Today, twenty years after the POSIX and ANSI C were published,
meillo@180	3612 developers can expect systems to comply with these standards.
meillo@121	3613 In consequence, MH-specific replacements for standard functions
meillo@121	3614 can and should be dropped.
meillo@121	3615 Kernighan and Pike advise: ``Use standard libraries.''
meillo@121	3616 .[ [
meillo@121	3617 kernighan pike practice of programming
meillo@121	3618 .], p. 196]
meillo@121	3619 Actually, MH had followed this advice in history,
meillo@121	3620 but it had not adjusted to the changes in this field.
meillo@121	3621 The
meillo@121	3622 .Fu snprintf()
meillo@121	3623 function, for instance, was standardized with C99 and is available
meillo@121	3624 almost everywhere because of its high usefulness.
meillo@180	3625 The project's own implementation of
meillo@121	3626 .Fu snprintf()
meillo@123	3627 was dropped in March 2012 in favor for using the one of the
meillo@123	3628 standard library.
meillo@123	3629 .Ci 0052f1024deb0a0a2fc2e5bacf93d45a5a9c9b32
meillo@123	3630 Such decisions limit the portability of mmh
meillo@173	3631 if systems do not support these standardized and widespread functions.
meillo@123	3632 This compromise is made because mmh focuses on the future.
meillo@121	3633 .P
meillo@180	3634 .\" XXX kuerzen und mit dem naechsten Absatz vereinen
meillo@180	3635 I am still in my twenties and my C and Unix experience comprises
meillo@123	3636 only half a dozen years.
meillo@121	3637 Hence, I need to learn about the history in retrospective.
meillo@121	3638 I have not used those ancient constructs myself.
meillo@121	3639 I have not suffered from their incompatibilities.
meillo@121	3640 I have not longed for standardization.
meillo@121	3641 All my programming experience is from a time when ANSI C and POSIX
meillo@121	3642 were well established already.
meillo@121	3643 I have only read a lot of books about the (good) old times.
meillo@180	3644 This puts me in a difficult position when working with old code.
meillo@123	3645 I need to freshly acquire knowledge about old code constructs and ancient
meillo@123	3646 programming styles, whereas older programmers know these things by
meillo@123	3647 heart from their own experience.
meillo@121	3648 .P
meillo@123	3649 Being aware of the situation, I rather let people with more historic
meillo@123	3650 experience replace ancient code constructs with standardized ones.
meillo@121	3651 Lyndon Nerenberg covered large parts of this task for the nmh project.
meillo@121	3652 He converted project-specific functions to POSIX replacements,
meillo@121	3653 also removing the conditionals compilation of now standardized features.
meillo@123	3654 Ken Hornstein and David Levine had their part in the work, too.
meillo@121	3655 Often, I only needed to pull over changes from nmh into mmh.
meillo@121	3656 These changes include many commits; these are among them:
meillo@121	3657 .Ci 768b5edd9623b7238e12ec8dfc409b82a1ed9e2d
meillo@121	3658 .Ci 0052f1024deb0a0a2fc2e5bacf93d45a5a9c9b32 .
meillo@102	3659 .P
meillo@123	3660 During my own work, I tidied up the \fIMH standard library\fP,
meillo@123	3661 .Fn libmh.a ,
meillo@123	3662 which is located in the
meillo@123	3663 .Fn sbr
meillo@123	3664 (``subroutines'') directory in the source tree.
meillo@123	3665 The MH library includes functions that mmh tools usually need.
meillo@123	3666 Among them are MH-specific functions for profile, context, sequence,
meillo@123	3667 and folder handling, but as well
meillo@123	3668 MH-independent functions, such as auxiliary string functions,
meillo@123	3669 portability interfaces and error-checking wrappers for critical
meillo@123	3670 functions of the standard library.
meillo@123	3671 .P
meillo@123	3672 I have replaced the
meillo@121	3673 .Fu atooi()
meillo@121	3674 function with calls to
meillo@123	3675 .Fu strtoul()
meillo@139	3676 with the third parameter, the base, set to eight.
meillo@121	3677 .Fu strtoul()
meillo@123	3678 is part of C89 and thus considered safe to use.
meillo@121	3679 .Ci c490c51b3c0f8871b6953bd0c74551404f840a74
meillo@102	3680 .P
meillo@121	3681 I did remove project-included fallback implementations of
meillo@121	3682 .Fu memmove()
meillo@121	3683 and
meillo@121	3684 .Fu strerror() ,
meillo@121	3685 although Peter Maydell had re-included them into nmh in 2008
meillo@121	3686 to support SunOS 4.
meillo@121	3687 Nevertheless, these functions are part of ANSI C.
meillo@121	3688 Systems that do not even provide full ANSI C support should not
meillo@121	3689 put a load on mmh.
meillo@121	3690 .Ci b067ff5c465a5d243ce5a19e562085a9a1a97215
meillo@121	3691 .P
meillo@121	3692 The
meillo@121	3693 .Fu copy()
meillo@180	3694 function copies the string in parameter one to the location in
meillo@180	3695 parameter two.
meillo@121	3696 In contrast to
meillo@121	3697 .Fu strcpy() ,
meillo@121	3698 it returns a pointer to the terminating null-byte in the destination area.
meillo@123	3699 The code was adjusted to replace
meillo@121	3700 .Fu copy()
meillo@123	3701 with
meillo@121	3702 .Fu strcpy() ,
meillo@121	3703 except within
meillo@121	3704 .Fu concat() ,
meillo@121	3705 where
meillo@121	3706 .Fu copy()
meillo@123	3707 was more convenient.
meillo@123	3708 Therefore, the definition of
meillo@121	3709 .Fu copy()
meillo@123	3710 was moved into the source file of
meillo@121	3711 .Fu concat()
meillo@123	3712 and its visibility is now limited to it.
meillo@121	3713 .Ci 552fd7253e5ee9e554c5c7a8248a6322aa4363bb
meillo@121	3714 .P
meillo@121	3715 The function
meillo@121	3716 .Fu r1bindex()
meillo@121	3717 had been a generalized version of
meillo@121	3718 .Fu basename()
meillo@121	3719 with minor differences.
meillo@121	3720 As all calls to
meillo@121	3721 .Fu r1bindex()
meillo@121	3722 had the slash (`/') as delimiter anyway,
meillo@121	3723 replacing
meillo@121	3724 .Fu r1bindex()
meillo@121	3725 with the more specific and better-named function
meillo@121	3726 .Fu basename()
meillo@121	3727 became desirable.
meillo@121	3728 Unfortunately, many of the 54 calls to
meillo@121	3729 .Fu r1bindex()
meillo@123	3730 depended on a special behavior,
meillo@121	3731 which differed from the POSIX specification for
meillo@121	3732 .Fu basename() .
meillo@121	3733 Hence,
meillo@121	3734 .Fu r1bindex()
meillo@121	3735 was kept but renamed to
meillo@123	3736 .Fu mhbasename() ,
meillo@123	3737 fixing the delimiter to the slash.
meillo@121	3738 .Ci 240013872c392fe644bd4f79382d9f5314b4ea60
meillo@121	3739 For possible uses of
meillo@121	3740 .Fu r1bindex()
meillo@121	3741 with a different delimiter,
meillo@121	3742 the ANSI C function
meillo@121	3743 .Fu strrchr()
meillo@121	3744 provides the core functionality.
meillo@121	3745 .P
meillo@121	3746 The
meillo@121	3747 .Fu ssequal()
meillo@121	3748 function \(en apparently for ``substring equal'' \(en
meillo@121	3749 was renamed to
meillo@121	3750 .Fu isprefix() ,
meillo@121	3751 because this is what it actually checks.
meillo@121	3752 .Ci c20b4fa14515c7ab388ce35411d89a7a92300711
meillo@121	3753 Its source file had included the following comments, no joke.
meillo@121	3754 .VS
meillo@121	3755 /*
meillo@121	3756 * THIS CODE DOES NOT WORK AS ADVERTISED.
meillo@121	3757 * It is actually checking if s1 is a PREFIX of s2.
meillo@121	3758 * All calls to this function need to be checked to see
meillo@121	3759 * if that needs to be changed. Prefix checking is cheaper, so
meillo@121	3760 * should be kept if it's sufficient.
meillo@121	3761 */
meillo@121	3762
meillo@121	3763 /*
meillo@121	3764 * Check if s1 is a substring of s2.
meillo@121	3765 * If yes, then return 1, else return 0.
meillo@121	3766 */
meillo@121	3767 VE
meillo@123	3768 Two months later, it was completely removed by replacing it with
meillo@123	3769 .Fu strncmp() .
meillo@123	3770 .Ci b0b1dd37ff515578cf7cba51625189eb34a196cb
meillo@121	3771
meillo@102	3772
meillo@102	3773
meillo@102	3774
meillo@133	3775
meillo@133	3776 .H2 "User Data Locations
meillo@133	3777 .P
meillo@133	3778 In nmh, a personal setup consists of the MH profile and the MH directory.
meillo@133	3779 The profile is a file named
meillo@133	3780 .Fn \&.mh_profile
meillo@133	3781 in the user's home directory.
meillo@133	3782 It contains the static configuration.
meillo@133	3783 It also contains the location of the MH directory in the profile entry
meillo@133	3784 .Pe Path .
meillo@133	3785 The MH directory contains the mail storage and is the first
meillo@133	3786 place to search for personal forms, scan formats, and similar
meillo@133	3787 configuration files.
meillo@133	3788 The location of the MH directory can be chosen freely by the user.
meillo@133	3789 The default and usual name is a directory named
meillo@133	3790 .Fn Mail
meillo@133	3791 in the home directory.
meillo@133	3792 .P
meillo@133	3793 The way MH data is splitted between profile and MH directory is a legacy.
meillo@133	3794 It is only sensible in a situation where the profile is the only
meillo@133	3795 configuration file.
meillo@133	3796 Why else should the mail storage and the configuration files be intermixed?
meillo@133	3797 They are different kinds of data:
meillo@133	3798 The data to be operated on and the configuration to change how
meillo@133	3799 tools operate.
meillo@180	3800 .\" XXX bad ... inapropriate?
meillo@133	3801 Splitting the configuration between the profile and the MH directory
meillo@133	3802 is bad.
meillo@133	3803 Merging the mail storage and the configuration in one directory is bad
meillo@133	3804 as well.
meillo@133	3805 As the mail storage and the configuration were not separated sensibly
meillo@133	3806 in the first place, I did it now.
meillo@133	3807 .P
meillo@133	3808 Personal mmh data is grouped by type, resulting in two distinct parts:
meillo@171	3809 the mail storage and the configuration.
meillo@133	3810 In mmh, the mail storage directory still contains all the messages,
meillo@133	3811 but, in exception of public sequences files, nothing else.
meillo@133	3812 In difference to nmh, the auxiliary configuration files are no longer
meillo@133	3813 located there.
meillo@133	3814 Therefore, the directory is no longer called the user's \fIMH directory\fP
meillo@133	3815 but his \fImail storage\fP.
meillo@133	3816 Its location is still user-chosen, with the default name
meillo@133	3817 .Fn Mail ,
meillo@133	3818 in the user's home directory.
meillo@133	3819 In mmh, the configuration is grouped together in
meillo@133	3820 the hidden directory
meillo@133	3821 .Fn \&.mmh
meillo@133	3822 in the user's home directory.
meillo@133	3823 This \fImmh directory\fP contains the context file, personal forms,
meillo@133	3824 scan formats, and the like, but also the user's profile, now named
meillo@133	3825 .Fn profile .
meillo@133	3826 The location of the profile is no longer fixed to
meillo@133	3827 .Fn $HOME/.mh_profile
meillo@133	3828 but to
meillo@133	3829 .Fn $HOME/.mmh/profile .
meillo@173	3830 Having both the file
meillo@133	3831 .Fn $HOME/.mh_profile
meillo@133	3832 and the configuration directory
meillo@133	3833 .Fn $HOME/.mmh
meillo@133	3834 appeared to be inconsistent.
meillo@133	3835 The approach chosen for mmh is consistent, simple, and familiar to
meillo@133	3836 Unix users.
meillo@168	3837 .Ci 7030d7edb099bff36ded7548bb5380f7acab4f9b
meillo@133	3838 .P
meillo@168	3839 MH allows users to have multiple MH setups.
meillo@133	3840 Therefore, it is necessary to select a different profile.
meillo@133	3841 The profile is the single entry point to access the rest of a
meillo@133	3842 personal MH setup.
meillo@133	3843 In nmh, the environment variable
meillo@133	3844 .Ev MH
meillo@133	3845 could be used to specifiy a different profile.
meillo@133	3846 To operate in the same MH setup with a separate context,
meillo@133	3847 the
meillo@133	3848 .Ev MHCONTEXT
meillo@133	3849 environment variable could be used.
meillo@133	3850 This allows having own current folders and current messages in
meillo@133	3851 each terminal, for instance.
meillo@133	3852 In mmh, three environment variables are used.
meillo@133	3853 .Ev MMH
meillo@133	3854 overrides the default location of the mmh directory (\c
meillo@133	3855 .Fn .mmh ).
meillo@133	3856 .Ev MMHP
meillo@133	3857 and
meillo@133	3858 .Ev MMHC
meillo@133	3859 override the paths to the profile and context files, respectively.
meillo@133	3860 This approach allows the set of personal configuration files to be chosen
meillo@133	3861 independently from the profile, context, and mail storage.
meillo@168	3862 .Ci 7030d7edb099bff36ded7548bb5380f7acab4f9b
meillo@133	3863 .P
meillo@133	3864 The separation of the files by type is sensible and convenient.
meillo@133	3865 The new approach has no functional disadvantages,
meillo@133	3866 as every setup I can imagine can be implemented with both approaches,
meillo@133	3867 possibly even easier with the new approach.
meillo@133	3868 The main achievement of the change is the clear and sensible split
meillo@133	3869 between mail storage and configuration.
meillo@133	3870
meillo@133	3871
meillo@133	3872
meillo@133	3873
meillo@133	3874
meillo@118	3875 .H2 "Modularization
meillo@118	3876 .P
meillo@123	3877 The source code of the mmh tools is located in the
meillo@122	3878 .Fn uip
meillo@123	3879 (``user interface programs'') directory.
meillo@180	3880 Each tool has a source file with the name of the command.
meillo@122	3881 For example,
meillo@122	3882 .Pn rmm
meillo@122	3883 is built from
meillo@122	3884 .Fn uip/rmm.c .
meillo@123	3885 Some source files are used for multiple programs.
meillo@122	3886 For example
meillo@122	3887 .Fn uip/scansbr.c
meillo@173	3888 is used for both
meillo@122	3889 .Pn scan
meillo@122	3890 and
meillo@122	3891 .Pn inc .
meillo@122	3892 In nmh, 49 tools were built from 76 source files.
meillo@123	3893 This is a ratio of 1.6 source files per program.
meillo@123	3894 32 programs depended on multiple source files;
meillo@123	3895 17 programs depended on one source file only.
meillo@122	3896 In mmh, 39 tools are built from 51 source files.
meillo@123	3897 This is a ratio of 1.3 source files per program.
meillo@123	3898 18 programs depend on multiple source files;
meillo@123	3899 21 programs depend on one source file only.
meillo@123	3900 (These numbers and the ones in the following text ignore the MH library
meillo@123	3901 as well as shell scripts and multiple names for the same program.)
meillo@180	3902 .\" XXX graph
meillo@122	3903 .P
meillo@123	3904 Splitting the source code of a large program into multiple files can
meillo@122	3905 increase the readability of its source code.
meillo@180	3906 .\" XXX however?
meillo@180	3907 Most of the mmh tools are simple and straight-forward programs.
meillo@122	3908 With the exception of the MIME handling tools,
meillo@122	3909 .Pn pick
meillo@179	3910 is the largest tool.
meillo@180	3911 It contains 1\\|037 lines of source code, excluding the MH library.
meillo@122	3912 Only the MIME handling tools (\c
meillo@122	3913 .Pn mhbuild ,
meillo@122	3914 .Pn mhstore ,
meillo@122	3915 .Pn show ,
meillo@122	3916 etc.)
meillo@122	3917 are larger.
meillo@122	3918 Splitting programs with less than 1\\|000 lines of code into multiple
meillo@123	3919 source files seldom leads to better readability.
meillo@123	3920 For such tools, splitting makes sense
meillo@122	3921 when parts of the code are reused in other programs,
meillo@179	3922 and the reused code fragment is (1) not general enough
meillo@179	3923 for including it in the MH library
meillo@179	3924 or (2) has dependencies on a library that only few programs need.
meillo@122	3925 .Fn uip/packsbr.c ,
meillo@122	3926 for instance, provides the core program logic for the
meillo@122	3927 .Pn packf
meillo@122	3928 and
meillo@122	3929 .Pn rcvpack
meillo@122	3930 programs.
meillo@122	3931 .Fn uip/packf.c
meillo@122	3932 and
meillo@122	3933 .Fn uip/rcvpack.c
meillo@122	3934 mainly wrap the core function appropriately.
meillo@122	3935 No other tools use the folder packing functions.
meillo@123	3936 As another example,
meillo@123	3937 .Fn uip/termsbr.c
meillo@123	3938 provides termcap support, which requires linking with a termcap or
meillo@123	3939 curses library.
meillo@123	3940 Including
meillo@123	3941 .Fn uip/termsbr.c
meillo@123	3942 into the MH library would require every program to be linked with
meillo@123	3943 termcap or curses, although only few of the programs require it.
meillo@122	3944 .P
meillo@122	3945 The task of MIME handling is complex enough that splitting its code
meillo@122	3946 into multiple source files improves the readability.
meillo@122	3947 The program
meillo@122	3948 .Pn mhstore ,
meillo@122	3949 for instance, is compiled out of seven source files with 2\\|500
meillo@122	3950 lines of code in summary.
meillo@122	3951 The main code file
meillo@122	3952 .Fn uip/mhstore.c
meillo@123	3953 consists of 800 lines; the other 1\\|700 lines of code are reused in
meillo@123	3954 other MIME handling tools.
meillo@123	3955 It seems to be worthwhile to bundle the generic MIME handling code into
meillo@123	3956 a MH-MIME library, as a companion to the MH standard library.
meillo@122	3957 This is left open for the future.
meillo@122	3958 .P
meillo@169	3959 The work already accomplished focussed on the non-MIME tools.
meillo@122	3960 The amount of code compiled into each program was reduced.
meillo@123	3961 This eases the understanding of the code base.
meillo@122	3962 In nmh,
meillo@122	3963 .Pn comp
meillo@122	3964 was built from six source files:
meillo@122	3965 .Fn comp.c ,
meillo@122	3966 .Fn whatnowproc.c ,
meillo@122	3967 .Fn whatnowsbr.c ,
meillo@122	3968 .Fn sendsbr.c ,
meillo@122	3969 .Fn annosbr.c ,
meillo@122	3970 and
meillo@122	3971 .Fn distsbr.c .
meillo@122	3972 In mmh, it builds from only two:
meillo@122	3973 .Fn comp.c
meillo@122	3974 and
meillo@122	3975 .Fn whatnowproc.c .
meillo@123	3976 In nmh's
meillo@123	3977 .Pn comp ,
meillo@123	3978 the core function of
meillo@122	3979 .Pn whatnow ,
meillo@122	3980 .Pn send ,
meillo@122	3981 and
meillo@122	3982 .Pn anno
meillo@123	3983 were compiled into
meillo@122	3984 .Pn comp .
meillo@123	3985 This saved the need to execute these programs with
meillo@122	3986 .Fu fork()
meillo@122	3987 and
meillo@122	3988 .Fu exec() ,
meillo@122	3989 two expensive system calls.
meillo@171	3990 Whereas this approach improved the time performance,
meillo@171	3991 it interwove the source code.
meillo@122	3992 Core functionalities were not encapsulated into programs but into
meillo@122	3993 function, which were then wrapped by programs.
meillo@122	3994 For example,
meillo@122	3995 .Fn uip/annosbr.c
meillo@122	3996 included the function
meillo@122	3997 .Fu annotate() .
meillo@122	3998 Each program that wanted to annotate messages, included the source file
meillo@123	3999 .Fn uip/annosbr.c
meillo@123	4000 and called
meillo@123	4001 .Fu annotate() .
meillo@123	4002 Because the function
meillo@123	4003 .Fu annotate()
meillo@123	4004 was used like the tool
meillo@123	4005 .Pn anno ,
meillo@123	4006 it had seven parameters, reflecting the command line switches of the tool.
meillo@122	4007 When another pair of command line switches was added to
meillo@122	4008 .Pn anno ,
meillo@122	4009 a rather ugly hack was implemented to avoid adding another parameter
meillo@122	4010 to the function.
meillo@122	4011 .Ci d9b1d57351d104d7ec1a5621f090657dcce8cb7f
meillo@122	4012 .P
meillo@122	4013 Separation simplifies the understanding of program code
meillo@122	4014 because the area influenced by any particular statement is smaller.
meillo@122	4015 The separating on the program-level is more strict than the separation
meillo@122	4016 on the function level.
meillo@122	4017 In mmh, the relevant code of
meillo@122	4018 .Pn comp
meillo@122	4019 comprises the two files
meillo@122	4020 .Fn uip/comp.c
meillo@122	4021 and
meillo@122	4022 .Fn uip/whatnowproc.c ,
meillo@123	4023 together 210 lines of code.
meillo@122	4024 In nmh,
meillo@122	4025 .Pn comp
meillo@122	4026 comprises six files with 2\\|450 lines.
meillo@123	4027 Not all of the code in these six files was actually used by
meillo@122	4028 .Pn comp ,
meillo@123	4029 but the code reader needed to read all of the code first to know which
meillo@123	4030 parts were used.
meillo@122	4031 .P
meillo@123	4032 As I have read a lot in the code base during the last two years,
meillo@123	4033 I learned about the easy and the difficult parts.
meillo@171	4034 Code is easy to understand if the influenced code area is small
meillo@171	4035 and its boundaries are strictly defined.
meillo@181	4036 Furthermore, the code needs to solve the problem in a straight-forward way.
meillo@123	4037 .P
meillo@123	4038 .\" XXX move this paragraph somewhere else?
meillo@123	4039 Reading
meillo@122	4040 .Pn rmm 's
meillo@122	4041 source code in
meillo@122	4042 .Fn uip/rmm.c
meillo@122	4043 is my recommendation for a beginner's entry point into the code base of nmh.
meillo@122	4044 The reasons are that the task of
meillo@122	4045 .Pn rmm
meillo@122	4046 is straight forward and it consists of one small source code file only,
meillo@122	4047 yet its source includes code constructs typical for MH tools.
meillo@122	4048 With the introduction of the trash folder in mmh,
meillo@122	4049 .Pn rmm
meillo@122	4050 became a bit more complex, because it invokes
meillo@122	4051 .Pn refile .
meillo@122	4052 Still, it is a good example for a simple tool with clear sources.
meillo@122	4053 .P
meillo@122	4054 Understanding
meillo@122	4055 .Pn comp
meillo@180	4056 .\" XXX kate fragen: more vs. as much
meillo@180	4057 requires to read 210 lines of code in mmh, but ten times more in nmh.
meillo@123	4058 Due to the aforementioned hack in
meillo@122	4059 .Pn anno
meillo@122	4060 to save the additional parameter, information passed through the program's
meillo@122	4061 source base in obscure ways.
meillo@123	4062 Thus, understanding
meillo@122	4063 .Pn comp ,
meillo@123	4064 required understanding the inner workings of
meillo@122	4065 .Fn uip/annosbr.c
meillo@122	4066 first.
meillo@123	4067 To be sure to fully understand a program, its whole source code needs
meillo@122	4068 to be examined.
meillo@123	4069 Not doing so is a leap of faith, assuming that the developers
meillo@122	4070 have avoided obscure programming techniques.
meillo@122	4071 By separating the tools on the program-level, the boundaries are
meillo@122	4072 clearly visible and technically enforced.
meillo@122	4073 The interfaces are calls to
meillo@122	4074 .Fu exec()
meillo@122	4075 rather than arbitrary function calls.
meillo@123	4076 .P
meillo@123	4077 But the real problem is another:
meillo@123	4078 Nmh violates the golden ``one tool, one job'' rule of the Unix philosophy.
meillo@181	4079 .\" XXX ref
meillo@123	4080 Understanding
meillo@122	4081 .Pn comp
meillo@123	4082 requires understanding
meillo@123	4083 .Fn uip/annosbr.c
meillo@123	4084 and
meillo@123	4085 .Fn uip/sendsbr.c
meillo@123	4086 because
meillo@123	4087 .Pn comp
meillo@123	4088 does annotate and send messages.
meillo@123	4089 In nmh, there surely exists the tool
meillo@122	4090 .Pn send ,
meillo@179	4091 which does mainly send messages.
meillo@123	4092 But
meillo@122	4093 .Pn comp
meillo@123	4094 and
meillo@122	4095 .Pn repl
meillo@122	4096 and
meillo@122	4097 .Pn forw
meillo@122	4098 and
meillo@122	4099 .Pn dist
meillo@122	4100 and
meillo@122	4101 .Pn whatnow
meillo@122	4102 and
meillo@123	4103 .Pn viamail ,
meillo@179	4104 they all (!) have the same message sending function included, as well.
meillo@123	4105 In result,
meillo@123	4106 .Pn comp
meillo@123	4107 sends messages without using
meillo@123	4108 .Pn send .
meillo@123	4109 The situation is the same as if
meillo@123	4110 .Pn grep
meillo@123	4111 would page without
meillo@123	4112 .Pn more
meillo@123	4113 just because both programs are part of the same code base.
meillo@123	4114 .P
meillo@173	4115 The clear separation on the surface \(en the tool chest approach \(en
meillo@123	4116 is violated on the level below.
meillo@122	4117 This violation is for the sake of time performance.
meillo@122	4118 On systems where
meillo@122	4119 .Fu fork()
meillo@122	4120 and
meillo@122	4121 .Fu exec()
meillo@122	4122 are expensive, the quicker response might be noticable.
meillo@124	4123 In the old times, sacrificing readability and conceptional beauty for
meillo@124	4124 speed might even have been a must to prevent MH from being unusably slow.
meillo@122	4125 Whatever the reasons had been, today they are gone.
meillo@123	4126 No longer should we sacrifice readability or conceptional beauty.
meillo@122	4127 No longer should we violate the Unix philosophy's ``one tool, one job''
meillo@122	4128 guideline.
meillo@181	4129 .\" XXX ref
meillo@123	4130 No longer should we keep speed improvements that became unnecessary.
meillo@122	4131 .P
meillo@123	4132 Therefore, mmh's
meillo@123	4133 .Pn comp
meillo@123	4134 does no longer send messages.
meillo@123	4135 In mmh, different jobs are divided among separate programs that
meillo@122	4136 invoke each other as needed.
meillo@123	4137 In consequence,
meillo@123	4138 .Pn comp
meillo@123	4139 invokes
meillo@123	4140 .Pn whatnow
meillo@123	4141 which thereafter invokes
meillo@123	4142 .Pn send .
meillo@168	4143 .Ci 3df5ab3c116e6d4a2fb4bb5cc9dfc5f781825815
meillo@168	4144 .Ci c73c00bfccd22ec77e9593f47462aeca4a8cd9c0
meillo@123	4145 The clear separation on the surface is maintained on the level below.
meillo@123	4146 Human users and the tools use the same interface \(en
meillo@123	4147 annotations, for example, are made by invoking
meillo@123	4148 .Pn anno ,
meillo@123	4149 no matter if requested by programs or by human beings.
meillo@168	4150 .Ci 469a4163c2a1a43731d412eaa5d9cae7d670c48b
meillo@168	4151 .Ci aed384169af5204b8002d06e7a22f89197963d2d
meillo@168	4152 .Ci 3caf9e298a8861729ca8b8a84f57022b6f3ea742
meillo@123	4153 The decrease of tools built from multiple source files and thus
meillo@123	4154 the decrease of
meillo@123	4155 .Fn uip/*sbr.c
meillo@123	4156 files confirm the improvement.
meillo@168	4157 .Ci 9e6d91313f01c96b4058d6bf419a8ca9a207bc33
meillo@168	4158 .ci 81744a46ac9f845d6c2b9908074d269275178d2e
meillo@168	4159 .Ci f0f858069d21111f0dbea510044593f89c9b0829
meillo@168	4160 .Ci 0503a6e9be34f24858b55b555a5c948182b9f24b
meillo@168	4161 .Ci 27826f9353e0f0b04590b7d0f8f83e60462b90f0
meillo@168	4162 .Ci d1da1f94ce62160aebb30df4063ccbc53768656b
meillo@168	4163 .Ci c42222869e318fff5dec395eca3e776db3075455
meillo@123	4164 .P
meillo@145	4165 .\" XXX move this paragraph up somewhere
meillo@123	4166 One disadvantage needs to be taken with this change:
meillo@123	4167 The compiler can no longer check the integrity of the interfaces.
meillo@123	4168 By changing the command line interfaces of tools, it is
meillo@123	4169 the developer's job to adjust the invocations of these tools as well.
meillo@123	4170 As this is a manual task and regression tests, which could detect such
meillo@124	4171 problems, are not available yet, it is prone to errors.
meillo@123	4172 These errors will not be detected at compile time but at run time.
meillo@171	4173 Installing regression tests is a pending task.
meillo@123	4174 In the best case, a uniform way of invoking tools from other tools
meillo@123	4175 can be developed to allow automated testing at compile time.
meillo@145	4176
meillo@145	4177
meillo@145	4178 .ig
meillo@145	4179 XXX consider writing about mhl vs. mhlproc
meillo@145	4180
meillo@145	4181 sbr/showfile.c
meillo@145	4182
meillo@145	4183 23 /*
meillo@145	4184 24 ** If you have your lproc listed as "mhl",
meillo@145	4185 25 ** then really invoked the mhlproc instead
meillo@145	4186 26 ** (which is usually mhl anyway).
meillo@145	4187 27 */
meillo@145	4188
meillo@145	4189 Sat Nov 24 19:09:14 1984 /mtr (agent: Marshall Rose) <uci@udel-dewey>
meillo@145	4190
meillo@145	4191 sbr/showfile.c: if lproc is "mhl", use mhlproc for consistency
meillo@145	4192 (Actually, user should use "lproc: show", "showproc: mhl".)
meillo@145	4193 ..