docs/master: discussion.roff annotate

docs/master

annotate discussion.roff @ 183:4c5055a0e981

Explained `hidden switches'.

author	markus schnalke <meillo@marmaro.de>
date	Wed, 11 Jul 2012 10:13:54 +0200
parents	764738b17b74
children	5360f5fdb118

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meillo@87	23 I believe that the development of all-in-one mail systems is obsolete.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