docs/master: discussion.roff annotate

docs/master

annotate discussion.roff @ 134:edf46861132b

Wrote about path conversion; Dropped the idea to write about scan listings

author	markus schnalke <meillo@marmaro.de>
date	Tue, 03 Jul 2012 22:30:20 +0200
parents	02660c14f6a8
children	470d5db0c06c

rev	line source
meillo@58	1 .H0 "Discussion
meillo@0	2 .P
meillo@58	3 This main chapter discusses the practical work done in the mmh project.
meillo@104	4 It is structured along the goals to achieve.
meillo@104	5 The concrete work done
meillo@58	6 is described in the examples of how the general goals were achieved.
meillo@87	7 The discussion compares the current version of mmh with the state of
meillo@87	8 nmh just before the mmh project started, i.e. Fall 2011.
meillo@87	9 Current changes of nmh will be mentioned only as side notes.
meillo@87	10 .\" XXX where do I discuss the parallel development of nmh?
meillo@58	11
meillo@58	12
meillo@58	13
meillo@133	14 .\" --------------------------------------------------------------
meillo@125	15 .H1 "Streamlining
meillo@58	16
meillo@0	17 .P
meillo@58	18 MH had been considered an all-in-one system for mail handling.
meillo@58	19 The community around nmh has a similar understanding.
meillo@87	20 In fundamental difference, mmh shall be a MUA only.
meillo@87	21 I believe that the development of all-in-one mail systems is obsolete.
meillo@87	22 Today, email is too complex to be fully covered by single projects.
meillo@87	23 Such a project won't be able to excel in all aspects.
meillo@87	24 Instead, the aspects of email should be covered my multiple projects,
meillo@87	25 which then can be combined to form a complete system.
meillo@87	26 Excellent implementations for the various aspects of email exist already.
meillo@87	27 Just to name three examples: Postfix is a specialized MTA,
meillo@87	28 Procmail is a specialized MDA, and Fetchmail is a specialized MRA.
meillo@89	29 I believe that it is best to use such specialized tools instead of
meillo@87	30 providing the same function again as a side-component in the project.
meillo@58	31 .P
meillo@87	32 Doing something well, requires to focus on a small set of specific aspects.
meillo@87	33 Under the assumption that focused development produces better results
meillo@100	34 in the particular area, specialized projects will be superior
meillo@87	35 in their field of focus.
meillo@87	36 Hence, all-in-one mail system projects \(en no matter if monolithic
meillo@87	37 or modular \(en will never be the best choice in any of the fields.
meillo@87	38 Even in providing the best consistent all-in-one system they are likely
meillo@87	39 to be beaten by projects that focus only on integrating existing mail
meillo@89	40 components to a homogeneous system.
meillo@87	41 .P
meillo@87	42 The limiting resource in Free Software community development
meillo@87	43 is usually man power.
meillo@87	44 If the development power is spread over a large development area,
meillo@87	45 it becomes even more difficult to compete with the specialists in the
meillo@87	46 various fields.
meillo@87	47 The concrete situation for MH-based mail systems is even tougher,
meillo@87	48 given the small and aged community, including both developers and users,
meillo@87	49 it has.
meillo@87	50 .P
meillo@87	51 In consequence, I believe that the available development resources
meillo@100	52 should focus on the point where MH is most unique.
meillo@87	53 This is clearly the user interface \(en the MUA.
meillo@125	54 Peripheral parts should be removed to streamline mmh for the MUA task.
meillo@60	55
meillo@60	56
meillo@100	57 .H2 "Mail Transfer Facilities
meillo@60	58 .P
meillo@60	59 In contrast to nmh, which also provides mail submission and mail retrieval
meillo@87	60 agents, mmh is a MUA only.
meillo@100	61 This general difference initiated the development of mmh.
meillo@66	62 Removing the mail transfer facilities had been the first work task
meillo@76	63 in the mmh project.
meillo@60	64 .P
meillo@105	65 Focusing on one mail agent role only is motivated by Eric Allman's
meillo@105	66 experience with Sendmail.
meillo@105	67 He identified limiting Sendmail the MTA task had be one reason for
meillo@105	68 its success:
meillo@105	69 .[ [
meillo@105	70 costales sendmail
meillo@105	71 .], p. xviii]
meillo@105	72 .QS
meillo@105	73 Second, I limited myself to the routing function \(en
meillo@110	74 I wouldn't write user agents or delivery back-ends.
meillo@105	75 This was a departure of the dominant through of the time,
meillo@105	76 in which routing logic, local delivery, and often the network code
meillo@105	77 were incorporated directly into the user agents.
meillo@105	78 .QE
meillo@105	79 .P
meillo@105	80 In mmh, the Mail Submission Agent (MSA) is called
meillo@105	81 \fIMessage Transfer Service\fP (MTS).
meillo@105	82 This facility, implemented by the
meillo@105	83 .Pn post
meillo@105	84 command, established network connections and spoke SMTP to submit
meillo@60	85 messages for relay to the outside world.
meillo@105	86 The changes in email demanded changes in this part of nmh too.
meillo@89	87 Encryption and authentication for network connections
meillo@87	88 needed to be supported, hence TLS and SASL were introduced into nmh.
meillo@87	89 This added complexity to nmh without improving it in its core functions.
meillo@87	90 Also, keeping up with recent developments in the field of
meillo@87	91 mail transfer requires development power and specialists.
meillo@87	92 In mmh this whole facility was simply cut off.
meillo@76	93 .Ci f6aa95b724fd8c791164abe7ee5468bf5c34f226
meillo@76	94 .Ci fecd5d34f65597a4dfa16aeabea7d74b191532c3
meillo@76	95 .Ci 156d35f6425bea4c1ed3c4c79783dc613379c65b
meillo@87	96 Instead, mmh depends on an external MSA.
meillo@60	97 The only outgoing interface available to mmh is the
meillo@60	98 .Pn sendmail
meillo@87	99 command, which almost any MSA provides.
meillo@87	100 If not, a wrapper program can be written.
meillo@87	101 It must read the message from the standard input, extract the
meillo@87	102 recipient addresses from the message header, and hand the message
meillo@87	103 over to the MSA.
meillo@87	104 For example, a wrapper script for qmail would be:
meillo@87	105 .VS
meillo@87	106 #!/bin/sh
meillo@87	107 # ignore command line arguments
meillo@87	108 exec qmail-inject
meillo@87	109 VE
meillo@87	110 The requirement to parse the recipient addresses out of the message header
meillo@87	111 is likely to be removed in the future.
meillo@87	112 Then mmh would give the recipient addresses as command line arguments.
meillo@100	113 This appears to be the better interface.
meillo@87	114 .\" XXX implement it
meillo@60	115 .P
meillo@60	116 To retrieve mail, the
meillo@60	117 .Pn inc
meillo@100	118 command acted as Mail Retrieval Agent (MRA).
meillo@100	119 It established network connections
meillo@76	120 and spoke POP3 to retrieve mail from remote servers.
meillo@76	121 As with mail submission, the network connections required encryption and
meillo@87	122 authentication, thus TLS and SASL were added.
meillo@87	123 Support for message retrieval through IMAP will become necessary
meillo@100	124 to be added soon, too, and likewise for any other changes in mail transfer.
meillo@100	125 Not so for mmh because it has dropped the support for retrieving mail
meillo@100	126 from remote locations.
meillo@76	127 .Ci ab7b48411962d26439f92f35ed084d3d6275459c
meillo@76	128 Instead, it depends on an external tool to cover this task.
meillo@100	129 In mmh exist two paths for messages to enter mmh's mail storage:
meillo@100	130 (1) Mail can be incorporated with
meillo@60	131 .Pn inc
meillo@87	132 from the system maildrop, or (2) with
meillo@60	133 .Pn rcvstore
meillo@87	134 by reading them, one at a time, from the standard input.
meillo@60	135 .P
meillo@60	136 With the removal of the MSA and MRA, mmh converted from an all-in-one
meillo@87	137 mail system to being a MUA only.
meillo@60	138 Now, of course, mmh depends on third-party software.
meillo@87	139 An external MSA is required to transfer mail to the outside world;
meillo@60	140 an external MRA is required to retrieve mail from remote machines.
meillo@60	141 There exist excellent implementations of such software,
meillo@76	142 which do this specific task likely better than the internal
meillo@87	143 versions had done it.
meillo@87	144 Also, the best suiting programs can be freely chosen.
meillo@60	145 .P
meillo@60	146 As it had already been possible to use an external MSA or MRA,
meillo@60	147 why not keep the internal version for convenience?
meillo@76	148 The question whether there is sense in having a fall-back pager in all
meillo@76	149 the command line tools, for the cases when
meillo@60	150 .Pn more
meillo@60	151 or
meillo@60	152 .Pn less
meillo@76	153 aren't available, appears to be ridiculous.
meillo@100	154 Of course, MSAs and MRAs are more complex than text pagers
meillo@87	155 and not necessarily available but still the concept of orthogonal
meillo@87	156 design holds: ``Write programs that do one thing and do it well.''
meillo@87	157 .[
meillo@87	158 mcilroy unix phil
meillo@87	159 p. 53
meillo@87	160 .]
meillo@87	161 .[
meillo@87	162 mcilroy bstj foreword
meillo@87	163 .]
meillo@87	164 Here, this part of the Unix philosophy was applied not only
meillo@87	165 to the programs but to the project itself.
meillo@87	166 In other words:
meillo@87	167 ``Develop projects that focus on one thing and do it well.''
meillo@87	168 Projects grown complex should be split for the same reasons programs grown
meillo@87	169 complex should be split.
meillo@100	170 If it is conceptionally more elegant to have the MSA and MRA as
meillo@87	171 separate projects then they should be separated.
meillo@87	172 This is the case here, in my opinion.
meillo@87	173 The RFCs propose this separation by clearly distinguishing the different
meillo@87	174 mail handling tasks.
meillo@87	175 .[
meillo@87	176 rfc 821
meillo@87	177 .]
meillo@87	178 The small interfaces between the mail agents support the separation.
meillo@76	179 .P
meillo@87	180 In the beginning, email had been small and simple.
meillo@100	181 At that time,
meillo@60	182 .Pn /bin/mail
meillo@100	183 had covered anything there was to email and still had been small
meillo@100	184 and simple.
meillo@100	185 Later, the essential complexity of email increased.
meillo@87	186 (Essential complexity is the complexity defined by the problem itself.\0
meillo@87	187 .[[
meillo@87	188 brooks no silver bullet
meillo@87	189 .]])
meillo@87	190 Email systems reacted to this change: They grew.
meillo@100	191 RFCs started to introduce the concept of mail agents to separate the
meillo@100	192 various tasks because they became more extensive and new tasks appeared.
meillo@100	193 As the mail systems grew even more, parts were split off.
meillo@100	194 In nmh, for instance, the POP server, which was included in the original
meillo@100	195 MH, was removed.
meillo@100	196 Now is the time to go one step further and split the MSA and MRA off, too.
meillo@87	197 Not only does this decrease the code size of the project,
meillo@87	198 but, more important, it unburdens mmh of the whole field of
meillo@87	199 message transfer with all its implications for the project.
meillo@100	200 There is no more need to concern with changes in network transfer.
meillo@76	201 This independence is received by depending on an external program
meillo@76	202 that covers the field.
meillo@76	203 Today, this is a reasonable exchange.
meillo@60	204 .P
meillo@100	205 Functionality can be added in three different ways:
meillo@87	206 .BU
meillo@87	207 Implementing the function originally in the project.
meillo@87	208 .BU
meillo@87	209 Depending on a library that provides the function.
meillo@87	210 .BU
meillo@87	211 Depending on a program that provides the function.
meillo@87	212 .P
meillo@87	213 Whereas adding the function originally to the project increases the
meillo@76	214 code size most and requires most maintenance and development work,
meillo@87	215 it makes the project most independent of other software.
meillo@87	216 Using libraries or external programs require less maintenance work
meillo@87	217 but introduces dependencies on external software.
meillo@87	218 Programs have the smallest interfaces and provide the best separation
meillo@87	219 but possibly limit the information exchange.
meillo@87	220 External libraries are stronger connected than external programs,
meillo@87	221 thus information can be exchanged more flexible.
meillo@87	222 Adding code to a project increases maintenance work.
meillo@87	223 .\" XXX ref
meillo@100	224 Implementing complex functions originally in the project adds
meillo@87	225 a lot of code.
meillo@87	226 This should be avoided if possible.
meillo@66	227 Hence, the dependencies only change in kind, not in their existence.
meillo@66	228 In mmh, library dependencies on
meillo@66	229 .Pn libsasl2
meillo@66	230 and
meillo@66	231 .Pn libcrypto /\c
meillo@66	232 .Pn libssl
meillo@66	233 were treated against program dependencies on an MSA and an MRA.
meillo@87	234 This also meant treating build-time dependencies against run-time
meillo@87	235 dependencies.
meillo@66	236 Besides program dependencies providing the stronger separation
meillo@66	237 and being more flexible, they also allowed
meillo@66	238 over 6\\|000 lines of code to be removed from mmh.
meillo@66	239 This made mmh's code base about 12\\|% smaller.
meillo@87	240 Reducing the project's code size by such an amount without actually
meillo@87	241 losing functionality is a convincing argument.
meillo@87	242 Actually, as external MSAs and MRAs are likely superior to the
meillo@87	243 project's internal versions, the common user even gains functionality.
meillo@66	244 .P
meillo@76	245 Users of MH should not have problems to set up an external MSA and MRA.
meillo@60	246 Also, the popular MSAs and MRAs have large communities and a lot
meillo@60	247 of documentation available.
meillo@87	248 Choices for MSAs range from full-featured MTAs like
meillo@60	249 .I Postfix
meillo@87	250 over mid-size MTAs like
meillo@60	251 .I masqmail
meillo@60	252 and
meillo@60	253 .I dma
meillo@60	254 to small forwarders like
meillo@60	255 .I ssmtp
meillo@60	256 and
meillo@60	257 .I nullmailer .
meillo@60	258 Choices for MRAs include
meillo@60	259 .I fetchmail ,
meillo@60	260 .I getmail ,
meillo@60	261 .I mpop
meillo@60	262 and
meillo@60	263 .I fdm .
meillo@60	264
meillo@60	265
meillo@100	266 .H2 "Non-MUA Tools
meillo@60	267 .P
meillo@87	268 One goal of mmh is to remove the tools that are not part of the MUA's task.
meillo@89	269 Further more, any tools that don't improve the MUA's job significantly
meillo@87	270 should be removed.
meillo@87	271 Loosely related and rarely used tools distract from the lean appearance.
meillo@87	272 They require maintenance work without adding much to the core task.
meillo@125	273 By removing these tools, the project shall become more streamlined
meillo@87	274 and focused.
meillo@76	275 In mmh the following tools are not available anymore:
meillo@62	276 .BU
meillo@58	277 .Pn conflict
meillo@87	278 was removed
meillo@76	279 .Ci 8b235097cbd11d728c07b966cf131aa7133ce5a9
meillo@87	280 because it is a mail system maintenance tool that is not MUA-related.
meillo@87	281 It even checked
meillo@58	282 .Fn /etc/passwd
meillo@58	283 and
meillo@58	284 .Fn /etc/group
meillo@87	285 for consistency, which is completely unrelated to email.
meillo@87	286 A tool like
meillo@87	287 .Pn conflict
meillo@87	288 is surely useful, but it should not be shipped with mmh.
meillo@76	289 .\" XXX historic reasons?
meillo@62	290 .BU
meillo@58	291 .Pn rcvtty
meillo@87	292 was removed
meillo@87	293 .Ci 14767c94b3827be7c867196467ed7aea5f6f49b0
meillo@89	294 because its use case of writing to the user's terminal
meillo@76	295 on receiving of mail is obsolete.
meillo@87	296 If users like to be informed of new mail, the shell's
meillo@58	297 .Ev MAILPATH
meillo@87	298 variable or graphical notifications are technically more appealing.
meillo@100	299 Writing directly to terminals is hardly ever wanted today.
meillo@62	300 If though one wants to have it this way, the standard tool
meillo@58	301 .Pn write
meillo@58	302 can be used in a way similar to:
meillo@82	303 .VS
meillo@58	304 scan -file - \| write `id -un`
meillo@82	305 VE
meillo@62	306 .BU
meillo@58	307 .Pn viamail
meillo@87	308 was removed
meillo@87	309 .Ci eda72d6a7a7c20ff123043fb7f19c509ea01f932
meillo@87	310 when the new attachment system was activated, because
meillo@58	311 .Pn forw
meillo@76	312 could then cover the task itself.
meillo@62	313 The program
meillo@58	314 .Pn sendfiles
meillo@62	315 was rewritten as a shell script wrapper around
meillo@58	316 .Pn forw .
meillo@76	317 .Ci 0e82199cf3c991a173e0ac8aa776efdb3ded61e6
meillo@62	318 .BU
meillo@58	319 .Pn msgchk
meillo@87	320 was removed
meillo@87	321 .Ci bb9360ead7eb7a3fedcce2eeedfc660014e41dbe ,
meillo@87	322 because it lost its use case when POP support was removed.
meillo@76	323 A call to
meillo@58	324 .Pn msgchk
meillo@87	325 provided hardly more information than:
meillo@82	326 .VS
meillo@58	327 ls -l /var/mail/meillo
meillo@82	328 VE
meillo@100	329 It did distinguish between old and new mail, but
meillo@100	330 this detail information can be retrieved with
meillo@76	331 .Pn stat (1),
meillo@62	332 too.
meillo@100	333 A small shell script could be written to print the information
meillo@76	334 in a similar way, if truly necessary.
meillo@76	335 As mmh's
meillo@76	336 .Pn inc
meillo@87	337 only incorporates mail from the user's local maildrop,
meillo@62	338 and thus no data transfers over slow networks are involved,
meillo@76	339 there's hardly any need to check for new mail before incorporating it.
meillo@62	340 .BU
meillo@58	341 .Pn msh
meillo@87	342 was removed
meillo@76	343 .Ci 916690191222433a6923a4be54b0d8f6ac01bd02
meillo@87	344 because the tool was in conflict with the philosophy of MH.
meillo@76	345 It provided an interactive shell to access the features of MH,
meillo@76	346 but it wasn't just a shell, tailored to the needs of mail handling.
meillo@76	347 Instead it was one large program that had several MH tools built in.
meillo@76	348 This conflicts with the major feature of MH of being a tool chest.
meillo@76	349 .Pn msh 's
meillo@76	350 main use case had been accessing Bulletin Boards, which have seized to
meillo@62	351 be popular.
meillo@62	352 .P
meillo@62	353 Removing
meillo@58	354 .Pn msh ,
meillo@76	355 together with the truly archaic code relicts
meillo@58	356 .Pn vmh
meillo@58	357 and
meillo@58	358 .Pn wmh ,
meillo@62	359 saved more than 7\\|000 lines of C code \(en
meillo@66	360 about 15\\|% of the project's original source code amount.
meillo@100	361 Having less code \(en with equal readability, of course \(en
meillo@76	362 for the same functionality is an advantage.
meillo@63	363 Less code means less bugs and less maintenance work.
meillo@76	364 As
meillo@63	365 .Pn rcvtty
meillo@63	366 and
meillo@63	367 .Pn msgchk
meillo@87	368 are assumed to be rarely used and can be implemented in different ways,
meillo@87	369 why should one keep them?
meillo@125	370 Removing them streamlines mmh.
meillo@63	371 .Pn viamail 's
meillo@63	372 use case is now partly obsolete and partly covered by
meillo@63	373 .Pn forw ,
meillo@76	374 hence there's no reason to still maintain it.
meillo@63	375 .Pn conflict
meillo@76	376 is not related to the mail client, and
meillo@63	377 .Pn msh
meillo@63	378 conflicts with the basic concept of MH.
meillo@76	379 Theses two tools might still be useful, but they should not be part of mmh.
meillo@63	380 .P
meillo@76	381 Finally, there's
meillo@76	382 .Pn slocal .
meillo@76	383 .Pn slocal
meillo@76	384 is an MDA and thus not directly MUA-related.
meillo@100	385 It should be removed from mmh, because including it conflicts with
meillo@100	386 the idea that mmh is a MUA only.
meillo@100	387 .Pn slocal
meillo@100	388 should rather become a separate project.
meillo@87	389 However,
meillo@76	390 .Pn slocal
meillo@76	391 provides rule-based processing of messages, like filing them into
meillo@76	392 different folders, which is otherwise not available in mmh.
meillo@87	393 Although
meillo@76	394 .Pn slocal
meillo@87	395 does neither pull in dependencies nor does it include a separate
meillo@100	396 technical area (cf. Sec. XXX), still,
meillo@100	397 it accounts for about 1\\|000 lines of code that need to be maintained.
meillo@76	398 As
meillo@76	399 .Pn slocal
meillo@76	400 is almost self-standing, it should be split off into a separate project.
meillo@76	401 This would cut the strong connection between the MUA mmh and the MDA
meillo@76	402 .Pn slocal .
meillo@87	403 For anyone not using MH,
meillo@87	404 .Pn slocal
meillo@87	405 would become yet another independent MDA, like
meillo@87	406 .I procmail .
meillo@100	407 Then
meillo@87	408 .Pn slocal
meillo@100	409 could be installed without the complete MH system.
meillo@76	410 Likewise, mmh users could decide to use
meillo@76	411 .I procmail
meillo@87	412 without having a second, unused MDA,
meillo@87	413 .Pn slocal ,
meillo@76	414 installed.
meillo@100	415 That appears to be conceptionally the best solution.
meillo@76	416 Yet,
meillo@76	417 .Pn slocal
meillo@87	418 is not split off.
meillo@100	419 I defer the decision over
meillo@78	420 .Pn slocal
meillo@100	421 in need for deeper investigation.
meillo@100	422 In the meanwhile, it remains part of mmh.
meillo@100	423 That does not hurt because
meillo@100	424 .Pn slocal
meillo@100	425 is unrelated to the rest of the project.
meillo@0	426
meillo@58	427
meillo@133	428
meillo@134	429 .H2 "Displaying Messages
meillo@131	430 .P
meillo@133	431 Since the very beginning, already in the first concept paper,
meillo@58	432 .Pn show
meillo@62	433 had been MH's message display program.
meillo@58	434 .Pn show
meillo@76	435 mapped message numbers and sequences to files and invoked
meillo@58	436 .Pn mhl
meillo@89	437 to have the files formatted.
meillo@88	438 With MIME, this approach wasn't sufficient anymore.
meillo@100	439 MIME messages can consist of multiple parts. Some parts are not
meillo@100	440 directly displayable and text content might be encoded in
meillo@58	441 foreign charsets.
meillo@58	442 .Pn show 's
meillo@76	443 understanding of messages and
meillo@58	444 .Pn mhl 's
meillo@88	445 display capabilities couldn't cope with the task any longer.
meillo@62	446 .P
meillo@88	447 Instead of extending these tools, additional tools were written from
meillo@88	448 scratch and added to the MH tool chest.
meillo@88	449 Doing so is encouraged by the tool chest approach.
meillo@88	450 Modular design is a great advantage for extending a system,
meillo@88	451 as new tools can be added without interfering with existing ones.
meillo@62	452 First, the new MIME features were added in form of the single program
meillo@58	453 .Pn mhn .
meillo@58	454 The command
meillo@82	455 .Cl "mhn -show 42
meillo@58	456 would show the MIME message numbered 42.
meillo@58	457 With the 1.0 release of nmh in February 1999, Richard Coleman finished
meillo@58	458 the split of
meillo@58	459 .Pn mhn
meillo@88	460 into a set of specialized tools, which together covered the
meillo@88	461 multiple aspects of MIME.
meillo@88	462 One of them was
meillo@69	463 .Pn mhshow ,
meillo@88	464 which replaced
meillo@88	465 .Cl "mhn -show" .
meillo@88	466 It was capable of displaying MIME messages appropriately.
meillo@62	467 .P
meillo@88	468 From then on, two message display tools were part of nmh,
meillo@76	469 .Pn show
meillo@76	470 and
meillo@76	471 .Pn mhshow .
meillo@88	472 To ease the life of users,
meillo@69	473 .Pn show
meillo@69	474 was extended to automatically hand the job over to
meillo@69	475 .Pn mhshow
meillo@69	476 if displaying the message would be beyond
meillo@69	477 .Pn show 's
meillo@69	478 abilities.
meillo@88	479 In consequence, the user would simply invoke
meillo@69	480 .Pn show
meillo@69	481 (possibly through
meillo@69	482 .Pn next
meillo@69	483 or
meillo@69	484 .Pn prev )
meillo@69	485 and get the message printed with either
meillo@69	486 .Pn show
meillo@69	487 or
meillo@69	488 .Pn mhshow ,
meillo@69	489 whatever was more appropriate.
meillo@69	490 .P
meillo@69	491 Having two similar tools for essentially the same task is redundant.
meillo@88	492 Usually,
meillo@88	493 users wouldn't distinguish between
meillo@88	494 .Pn show
meillo@88	495 and
meillo@88	496 .Pn mhshow
meillo@88	497 in their daily mail reading.
meillo@88	498 Having two separate display programs was therefore mainly unnecessary
meillo@88	499 from a user's point of view.
meillo@88	500 Besides, the development of both programs needed to be in sync,
meillo@76	501 to ensure that the programs behaved in a similar way,
meillo@76	502 because they were used like a single tool.
meillo@76	503 Different behavior would have surprised the user.
meillo@69	504 .P
meillo@69	505 Today, non-MIME messages are rather seen to be a special case of
meillo@100	506 MIME messages, although it is the other way round.
meillo@69	507 As
meillo@69	508 .Pn mhshow
meillo@88	509 had already be able to display non-MIME messages, it appeared natural
meillo@69	510 to drop
meillo@69	511 .Pn show
meillo@69	512 in favor of using
meillo@69	513 .Pn mhshow
meillo@69	514 exclusively.
meillo@88	515 .Ci 4c1efddfd499300c7e74263e57d8aa137e84c853
meillo@88	516 Removing
meillo@88	517 .Pn show
meillo@88	518 is no loss in function, because functionally
meillo@88	519 .Pn mhshow
meillo@88	520 covers it completely.
meillo@88	521 The old behavior of
meillo@88	522 .Pn show
meillo@88	523 can still be emulated with the simple command line:
meillo@88	524 .VS
meillo@88	525 mhl `mhpath c`
meillo@88	526 VE
meillo@88	527 .P
meillo@76	528 For convenience,
meillo@76	529 .Pn mhshow
meillo@88	530 was renamed to
meillo@88	531 .Pn show
meillo@88	532 after
meillo@88	533 .Pn show
meillo@88	534 was gone.
meillo@88	535 It is clear that such a rename may confuse future developers when
meillo@88	536 trying to understand the history.
meillo@88	537 Nevertheless, I consider the convenience on the user's side,
meillo@88	538 to call
meillo@88	539 .Pn show
meillo@88	540 when they want a message to be displayed, to outweigh the inconvenience
meillo@88	541 on the developer's side when understanding the project history.
meillo@69	542 .P
meillo@88	543 To prepare for the transition,
meillo@69	544 .Pn mhshow
meillo@69	545 was reworked to behave more like
meillo@69	546 .Pn show
meillo@69	547 first.
meillo@88	548 (cf. Sec. XXX)
meillo@88	549 Once the tools behaved more alike, the replacing appeared to be
meillo@88	550 even more natural.
meillo@88	551 Today, mmh's new
meillo@69	552 .Pn show
meillo@88	553 became the one single message display program again, with the difference
meillo@88	554 that today it handles MIME messages as well as non-MIME messages.
meillo@88	555 The outcome of the transition is one program less to maintain,
meillo@88	556 no second display program for users to deal with,
meillo@88	557 and less system complexity.
meillo@69	558 .P
meillo@88	559 Still, removing the old
meillo@69	560 .Pn show
meillo@88	561 hurts in one regard: It had been such a simple program.
meillo@88	562 Its lean elegance is missing to the new
meillo@69	563 .Pn show .
meillo@88	564 But there is no chance;
meillo@88	565 supporting MIME demands for higher essential complexity.
meillo@58	566
meillo@134	567 .ig
meillo@134	568 XXX
meillo@134	569 Consider including text on scan listings here
meillo@58	570
meillo@134	571 Scan listings shall not contain body content. Hence, removed this feature.
meillo@134	572 Scan listings shall operator on message headers and non-message information
meillo@134	573 only. Displaying the beginning of the body complicates everything too much.
meillo@134	574 That's no surprise, because it's something completely different. If you
meillo@134	575 want to examine the body, then use show(1)/mhshow(1).
meillo@134	576 Changed the default scan formats accordingly.
meillo@134	577 .Ci 70b2643e0da8485174480c644ad9785c84f5bff4
meillo@134	578 ..
meillo@131	579
meillo@131	580
meillo@131	581
meillo@133	582
meillo@100	583 .H2 "Configure Options
meillo@58	584 .P
meillo@76	585 Customization is a double-edged sword.
meillo@76	586 It allows better suiting setups, but not for free.
meillo@76	587 There is the cost of code complexity to be able to customize.
meillo@76	588 There is the cost of less tested setups, because there are
meillo@72	589 more possible setups and especially corner-cases.
meillo@76	590 And, there is the cost of choice itself.
meillo@76	591 The code complexity directly affects the developers.
meillo@72	592 Less tested code affects both, users and developers.
meillo@76	593 The problem of choice affects the users, for once by having to
meillo@100	594 choose, but also by more complex interfaces that require more documentation.
meillo@72	595 Whenever options add little advantages, they should be considered for
meillo@72	596 removal.
meillo@72	597 I have reduced the number of project-specific configure options from
meillo@72	598 fifteen to three.
meillo@74	599
meillo@76	600 .U3 "Mail Transfer Facilities
meillo@74	601 .P
meillo@85	602 With the removal of the mail transfer facilities five configure
meillo@85	603 options vanished:
meillo@85	604 .P
meillo@85	605 The switches
meillo@85	606 .Sw --with-tls
meillo@85	607 and
meillo@85	608 .Sw --with-cyrus-sasl
meillo@89	609 had activated the support for transfer encryption and authentication.
meillo@85	610 This is not needed anymore.
meillo@85	611 .Ci fecd5d34f65597a4dfa16aeabea7d74b191532c3
meillo@85	612 .Ci 156d35f6425bea4c1ed3c4c79783dc613379c65b
meillo@85	613 .P
meillo@85	614 The configure switch
meillo@85	615 .Sw --enable-pop
meillo@85	616 activated the message retrieval facility.
meillo@85	617 The code area that would be conditionally compiled in for TLS and SASL
meillo@85	618 support had been small.
meillo@85	619 The conditionally compiled code area for POP support had been much larger.
meillo@85	620 Whereas the code base changes would only slightly change on toggling
meillo@85	621 TLS or SASL support, it changed much on toggling POP support.
meillo@85	622 The changes in the code base could hardly be overviewed.
meillo@85	623 By having POP support togglable a second code base had been created,
meillo@85	624 one that needed to be tested.
meillo@85	625 This situation is basically similar for the conditional TLS and SASL
meillo@85	626 code, but there the changes are minor and can yet be overviewed.
meillo@85	627 Still, conditional compilation of a code base creates variations
meillo@85	628 of the original program.
meillo@85	629 More variations require more testing and maintenance work.
meillo@85	630 .P
meillo@85	631 Two other options only specified default configuration values:
meillo@100	632 .Sw --with-mts
meillo@100	633 defined the default transport service, either
meillo@100	634 .Ar smtp
meillo@100	635 or
meillo@100	636 .Ar sendmail .
meillo@85	637 In mmh this fixed to
meillo@85	638 .Ar sendmail .
meillo@85	639 .Ci f6aa95b724fd8c791164abe7ee5468bf5c34f226
meillo@85	640 With
meillo@100	641 .Sw --with-smtpservers
meillo@85	642 default SMTP servers for the
meillo@85	643 .Ar smtp
meillo@85	644 transport service could be specified.
meillo@72	645 .Ci 128545e06224233b7e91fc4c83f8830252fe16c9
meillo@85	646 Both of them became irrelevant.
meillo@72	647
meillo@74	648 .U3 "Backup Prefix
meillo@74	649 .P
meillo@76	650 The backup prefix is the string that was prepended to message
meillo@76	651 filenames to tag them as deleted.
meillo@76	652 By default it had been the comma character `\f(CW,\fP'.
meillo@78	653 In July 2000, Kimmo Suominen introduced
meillo@78	654 the configure option
meillo@78	655 .Sw --with-hash-backup
meillo@78	656 to change the default to the hash symbol `\f(CW#\fP'.
meillo@78	657 The choice was probably personal preference, because first, the
meillo@78	658 option was named
meillo@78	659 .Sw --with-backup-prefix.
meillo@78	660 and had the prefix symbol as argument.
meillo@100	661 But giving the hash symbol as argument caused too many problems
meillo@100	662 for Autoconf,
meillo@100	663 thus the option was limited to use the hash symbol as the default prefix.
meillo@100	664 This supports the assumption, that the choice for the hash was
meillo@100	665 personal preference only.
meillo@100	666 Being related or not, words that start with the hash symbol
meillo@78	667 introduce a comment in the Unix shell.
meillo@72	668 Thus, the command line
meillo@72	669 .Cl "rm #13 #15
meillo@72	670 calls
meillo@72	671 .Pn rm
meillo@72	672 without arguments because the first hash symbol starts the comment
meillo@72	673 that reaches until the end of the line.
meillo@72	674 To delete the backup files,
meillo@72	675 .Cl "rm ./#13 ./#15"
meillo@72	676 needs to be used.
meillo@100	677 Using the hash as backup prefix can be seen as a precaution against
meillo@78	678 data loss.
meillo@78	679 .P
meillo@72	680 I removed the configure option but added the profile entry
meillo@72	681 .Pe backup-prefix ,
meillo@72	682 which allows to specify an arbitrary string as backup prefix.
meillo@72	683 .Ci 6c40d481d661d532dd527eaf34cebb6d3f8ed086
meillo@76	684 Profile entries are the common method to change mmh's behavior.
meillo@76	685 This change did not remove the choice but moved it to a location where
meillo@72	686 it suited better.
meillo@76	687 .P
meillo@78	688 Eventually, however, the new trash folder concept
meillo@78	689 .Cf "Sec. XXX
meillo@78	690 obsoleted the concept of the backup prefix completely.
meillo@78	691 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@133	692 .Ci ca0b3e830b86700d9e5e31b1784de2bdcaf58fc5
meillo@133	693
meillo@76	694
meillo@76	695 .U3 "Editor and Pager
meillo@74	696 .P
meillo@74	697 The two configure options
meillo@74	698 .CW --with-editor=EDITOR
meillo@74	699 .CW --with-pager=PAGER
meillo@74	700 were used to specify the default editor and pager at configure time.
meillo@109	701 Doing so at configure time made sense in the eighties,
meillo@76	702 when the set of available editors and pagers varied much across
meillo@76	703 different systems.
meillo@89	704 Today, the situation is more homogeneous.
meillo@74	705 The programs
meillo@74	706 .Pn vi
meillo@74	707 and
meillo@74	708 .Pn more
meillo@76	709 can be expected to be available on every Unix system,
meillo@74	710 as they are specified by POSIX since two decades.
meillo@74	711 (The specifications for
meillo@74	712 .Pn vi
meillo@74	713 and
meillo@74	714 .Pn more
meillo@74	715 appeared in
meillo@74	716 .[
meillo@74	717 posix 1987
meillo@74	718 .]
meillo@74	719 and,
meillo@74	720 .[
meillo@74	721 posix 1992
meillo@74	722 .]
meillo@74	723 respectively.)
meillo@74	724 As a first step, these two tools were hard-coded as defaults.
meillo@74	725 .Ci 5d43a99db70c12a673028c7758c20cbe3e13ef5f
meillo@74	726 Not changed were the
meillo@74	727 .Pe editor
meillo@74	728 and
meillo@74	729 .Pe moreproc
meillo@76	730 profile entries, which allowed the user to override the system defaults.
meillo@74	731 Later, the concept was reworked to respect the standard environment
meillo@74	732 variables
meillo@74	733 .Ev VISUAL
meillo@74	734 and
meillo@74	735 .Ev PAGER
meillo@76	736 if they are set.
meillo@74	737 Today, mmh determines the editor to use in the following order,
meillo@74	738 taking the first available and non-empty item:
meillo@74	739 .IP (1)
meillo@74	740 Environment variable
meillo@74	741 .Ev MMHEDITOR
meillo@74	742 .IP (2)
meillo@74	743 Profile entry
meillo@74	744 .Pe Editor
meillo@74	745 .IP (3)
meillo@74	746 Environment variable
meillo@74	747 .Ev VISUAL
meillo@74	748 .IP (4)
meillo@74	749 Environment variable
meillo@74	750 .Ev EDITOR
meillo@74	751 .IP (5)
meillo@74	752 Command
meillo@74	753 .Pn vi .
meillo@74	754 .P
meillo@76	755 .Ci f85f4b7ae62e3d05a945dcd46ead51f0a2a89a9b
meillo@76	756 .P
meillo@89	757 The pager to use is determined in a similar order,
meillo@74	758 also taking the first available and non-empty item:
meillo@74	759 .IP (1)
meillo@74	760 Environment variable
meillo@74	761 .Ev MMHPAGER
meillo@74	762 .IP (2)
meillo@74	763 Profile entry
meillo@74	764 .Pe Pager
meillo@74	765 (replaces
meillo@74	766 .Pe moreproc )
meillo@74	767 .IP (3)
meillo@74	768 Environment variable
meillo@74	769 .Ev PAGER
meillo@74	770 .IP (4)
meillo@74	771 Command
meillo@74	772 .Pn more .
meillo@74	773 .P
meillo@74	774 .Ci 0c4214ea2aec6497d0d67b436bbee9bc1d225f1e
meillo@74	775 .P
meillo@76	776 By respecting the
meillo@74	777 .Ev VISUAL /\c
meillo@74	778 .Ev EDITOR
meillo@74	779 and
meillo@74	780 .Ev PAGER
meillo@76	781 environment variables,
meillo@76	782 the new behavior confirms better to the common style on Unix systems.
meillo@76	783 Additionally, the new approach is more uniform and clearer to users.
meillo@72	784
meillo@72	785
meillo@76	786 .U3 "ndbm
meillo@72	787 .P
meillo@74	788 .Pn slocal
meillo@78	789 used to depend on
meillo@74	790 .I ndbm ,
meillo@74	791 a database library.
meillo@76	792 The database is used to store the `\fLMessage-ID\fP's of all
meillo@76	793 messages delivered.
meillo@74	794 This enables
meillo@74	795 .Pn slocal
meillo@74	796 to suppress delivering the same message to the same user twice.
meillo@74	797 (This features was enabled by the
meillo@74	798 .Sw -suppressdup
meillo@74	799 switch.)
meillo@74	800 .P
meillo@100	801 A variety of versions of the database library exist.
meillo@78	802 .[
meillo@78	803 wolter unix incompat notes dbm
meillo@78	804 .]
meillo@74	805 Complicated autoconf code was needed to detect them correctly.
meillo@74	806 Further more, the configure switches
meillo@74	807 .Sw --with-ndbm=ARG
meillo@74	808 and
meillo@74	809 .Sw --with-ndbmheader=ARG
meillo@74	810 were added to help with difficult setups that would
meillo@78	811 not be detected automatically or correctly.
meillo@74	812 .P
meillo@74	813 By removing the suppress duplicates feature of
meillo@74	814 .Pn slocal ,
meillo@74	815 the dependency on
meillo@74	816 .I ndbm
meillo@78	817 vanished and 120 lines of complex autoconf code could be saved.
meillo@74	818 .Ci ecd6d6a20cb7a1507e3a20d6c4cb3a1cf14c6bbf
meillo@89	819 The change removed functionality too, but that is minor to the
meillo@78	820 improvement by dropping the dependency and the complex autoconf code.
meillo@72	821
meillo@74	822 .U3 "mh-e Support
meillo@72	823 .P
meillo@74	824 The configure option
meillo@74	825 .Sw --disable-mhe
meillo@74	826 was removed when the mh-e support was reworked.
meillo@74	827 Mh-e is the Emacs front-end to MH.
meillo@76	828 It requires MH to provide minor additional functions.
meillo@76	829 The
meillo@76	830 .Sw --disable-mhe
meillo@76	831 configure option could switch these extensions off.
meillo@76	832 After removing the support for old versions of mh-e,
meillo@74	833 only the
meillo@74	834 .Sw -build
meillo@76	835 switches of
meillo@74	836 .Pn forw
meillo@74	837 and
meillo@74	838 .Pn repl
meillo@76	839 are left to be mh-e extensions.
meillo@76	840 They are now always built in because they add little code and complexity.
meillo@76	841 In consequence, the
meillo@74	842 .Sw --disable-mhe
meillo@76	843 configure option was removed
meillo@72	844 .Ci a7ce7b4a580d77b6c2c4d980812beb589aa4c643
meillo@74	845 Removing the option removed a second code setup that would have
meillo@74	846 needed to be tested.
meillo@76	847 This change was first done in nmh and thereafter merged into mmh.
meillo@76	848 .P
meillo@76	849 The interface changes in mmh require mh-e to be adjusted in order
meillo@76	850 to be able to use mmh as back-end.
meillo@76	851 This will require minor changes to mh-e, but removing the
meillo@76	852 .Sw -build
meillo@76	853 switches would require more rework.
meillo@72	854
meillo@74	855 .U3 "Masquerading
meillo@72	856 .P
meillo@74	857 The configure option
meillo@74	858 .Sw --enable-masquerade
meillo@76	859 could take up to three arguments:
meillo@76	860 `draft_from', `mmailid', and `username_extension'.
meillo@74	861 They activated different types of address masquerading.
meillo@74	862 All of them were implemented in the SMTP-speaking
meillo@74	863 .Pn post
meillo@76	864 command, which provided an MSA.
meillo@76	865 Address masquerading is an MTA's task and mmh does not cover
meillo@76	866 this field anymore.
meillo@76	867 Hence, true masquerading needs to be implemented in the external MTA.
meillo@74	868 .P
meillo@74	869 The
meillo@74	870 .I mmailid
meillo@74	871 masquerading type is the oldest one of the three and the only one
meillo@74	872 available in the original MH.
meillo@74	873 It provided a
meillo@74	874 .I username
meillo@74	875 to
meillo@74	876 .I fakeusername
meillo@76	877 mapping, based on the password file's GECOS field.
meillo@74	878 The man page
meillo@74	879 .Mp mh-tailor(5)
meillo@74	880 described the use case as being the following:
meillo@98	881 .QS
meillo@74	882 This is useful if you want the messages you send to always
meillo@74	883 appear to come from the name of an MTA alias rather than your
meillo@74	884 actual account name. For instance, many organizations set up
meillo@74	885 `First.Last' sendmail aliases for all users. If this is
meillo@74	886 the case, the GECOS field for each user should look like:
meillo@74	887 ``First [Middle] Last <First.Last>''
meillo@98	888 .QE
meillo@74	889 .P
meillo@74	890 As mmh sends outgoing mail via the local MTA only,
meillo@76	891 the best location to do such global rewrites is there.
meillo@74	892 Besides, the MTA is conceptionally the right location because it
meillo@74	893 does the reverse mapping for incoming mail (aliasing), too.
meillo@76	894 Further more, masquerading set up there is readily available for all
meillo@74	895 mail software on the system.
meillo@76	896 Hence, mmailid masquerading was removed.
meillo@74	897 .Ci 0836c8000ccb34b59410ef1c15b1b7feac70ce5f
meillo@74	898 .P
meillo@74	899 The
meillo@74	900 .I username_extension
meillo@76	901 masquerading type did not replace the username but would append a suffix,
meillo@76	902 specified by the
meillo@74	903 .Ev USERNAME_EXTENSION
meillo@76	904 environment variable, to it.
meillo@76	905 This provided support for the
meillo@74	906 .I user-extension
meillo@74	907 feature of qmail and the similar
meillo@74	908 .I "plussed user
meillo@74	909 processing of sendmail.
meillo@74	910 The decision to remove this username_extension masquerading was
meillo@74	911 motivated by the fact that
meillo@74	912 .Pn spost
meillo@76	913 hadn't supported it already.
meillo@76	914 .Ci 2abae0bfd0ad5bf898461e50aa4b466d641f23d9
meillo@76	915 Username extensions are possible in mmh, but less convenient to use.
meillo@76	916 .\" XXX format file %(getenv USERNAME_EXTENSION)
meillo@74	917 .P
meillo@74	918 The
meillo@74	919 .I draft_from
meillo@74	920 masquerading type instructed
meillo@74	921 .Pn post
meillo@84	922 to use the value of the
meillo@84	923 .Hd From
meillo@84	924 header field as SMTP envelope sender.
meillo@76	925 Sender addresses could be replaced completely.
meillo@74	926 .Ci b14ea6073f77b4359aaf3fddd0e105989db9
meillo@76	927 Mmh offers a kind of masquerading similar in effect, but
meillo@74	928 with technical differences.
meillo@76	929 As mmh does not transfer messages itself, the local MTA has final control
meillo@76	930 over the sender's address. Any masquerading mmh introduces may be reverted
meillo@76	931 by the MTA.
meillo@76	932 In times of pedantic spam checking, an MTA will take care to use
meillo@76	933 sensible envelope sender addresses to keep its own reputation up.
meillo@84	934 Nonetheless, the MUA can set the
meillo@84	935 .Hd From
meillo@84	936 header field and thereby propose
meillo@76	937 a sender address to the MTA.
meillo@74	938 The MTA may then decide to take that one or generate the canonical sender
meillo@74	939 address for use as envelope sender address.
meillo@74	940 .P
meillo@74	941 In mmh, the MTA will always extract the recipient and sender from the
meillo@84	942 message header (\c
meillo@74	943 .Pn sendmail 's
meillo@74	944 .Sw -t
meillo@74	945 switch).
meillo@84	946 The
meillo@84	947 .Hd From
meillo@84	948 header field of the draft may be set arbitrary by the user.
meillo@74	949 If it is missing, the canonical sender address will be generated by the MTA.
meillo@74	950
meillo@74	951 .U3 "Remaining Options
meillo@74	952 .P
meillo@74	953 Two configure options remain in mmh.
meillo@74	954 One is the locking method to use:
meillo@74	955 .Sw --with-locking=[dot\|fcntl\|flock\|lockf] .
meillo@76	956 The idea of removing all methods except the portable dot locking
meillo@76	957 and having that one as the default is appealing, but this change
meillo@76	958 requires deeper technical investigation into the topic.
meillo@76	959 The other option,
meillo@74	960 .Sw --enable-debug ,
meillo@74	961 compiles the programs with debugging symbols and does not strip them.
meillo@74	962 This option is likely to stay.
meillo@72	963
meillo@72	964
meillo@58	965
meillo@63	966
meillo@100	967 .H2 "Command Line Switches
meillo@58	968 .P
meillo@93	969 The command line switches of MH tools follow the X Window style.
meillo@93	970 They are words, introduced by a single dash.
meillo@93	971 For example:
meillo@93	972 .Cl "-truncate" .
meillo@93	973 Every program in mmh has two generic switches:
meillo@93	974 .Sw -help ,
meillo@93	975 to print a short message on how to use the program, and
meillo@93	976 .Sw -Version ,
meillo@93	977 to tell what version of mmh the program belongs to.
meillo@93	978 .P
meillo@93	979 Switches change the behavior of programs.
meillo@93	980 Programs that do one thing in one way require no switches.
meillo@93	981 In most cases, doing something in exactly one way is too limiting.
meillo@97	982 If there is basically one task to accomplish, but it should be done
meillo@93	983 in various ways, switches are a good approach to alter the behavior
meillo@93	984 of a program.
meillo@93	985 Changing the behavior of programs provides flexibility and customization
meillo@97	986 to users, but at the same time it complicates the code, documentation and
meillo@93	987 usage of the program.
meillo@97	988 .\" XXX: Ref
meillo@93	989 Therefore, the number of switches should be kept small.
meillo@93	990 A small set of well-chosen switches does no harm.
meillo@93	991 But usually, the number of switches increases over time.
meillo@93	992 Already in 1985, Rose and Romine have identified this as a major
meillo@93	993 problem of MH:
meillo@93	994 .[ [
meillo@93	995 rose romine real work
meillo@93	996 .], p. 12]
meillo@98	997 .QS
meillo@93	998 A complaint often heard about systems which undergo substantial development
meillo@93	999 by many people over a number of years, is that more and more options are
meillo@93	1000 introduced which add little to the functionality but greatly increase the
meillo@93	1001 amount of information a user needs to know in order to get useful work done.
meillo@93	1002 This is usually referred to as creeping featurism.
meillo@93	1003 .QP
meillo@93	1004 Unfortunately MH, having undergone six years of off-and-on development by
meillo@93	1005 ten or so well-meaning programmers (the present authors included),
meillo@93	1006 suffers mightily from this.
meillo@98	1007 .QE
meillo@93	1008 .P
meillo@97	1009 Being reluctant to adding new switches \(en or `options',
meillo@97	1010 as Rose and Romine call them \(en is one part of a counter-action,
meillo@97	1011 the other part is removing hardly used switches.
meillo@97	1012 Nmh's tools had lots of switches already implemented,
meillo@97	1013 hence, cleaning up by removing some of them was the more important part
meillo@97	1014 of the counter-action.
meillo@93	1015 Removing existing functionality is always difficult because it
meillo@93	1016 breaks programs that use these functions.
meillo@93	1017 Also, for every obsolete feature, there'll always be someone who still
meillo@93	1018 uses it and thus opposes its removal.
meillo@93	1019 This puts the developer into the position,
meillo@93	1020 where sensible improvements to style are regarded as destructive acts.
meillo@97	1021 Yet, living with the featurism is far worse, in my eyes, because
meillo@97	1022 future needs will demand adding further features,
meillo@93	1023 worsening the situation more and more.
meillo@93	1024 Rose and Romine added in a footnote,
meillo@93	1025 ``[...]
meillo@93	1026 .Pn send
meillo@93	1027 will no doubt acquire an endless number of switches in the years to come.''
meillo@97	1028 Although clearly humorous, the comment points to the nature of the problem.
meillo@97	1029 Refusing to add any new switches would encounter the problem at its root,
meillo@97	1030 but this is not practical.
meillo@97	1031 New needs will require new switches and it would be unwise to block
meillo@97	1032 them strictly.
meillo@97	1033 Nevertheless, removing obsolete switches still is an effective approach
meillo@97	1034 to deal with the problem.
meillo@97	1035 Working on an experimental branch without an established user base,
meillo@97	1036 eased my work because I did not offend users when I removed existing
meillo@110	1037 functions.
meillo@93	1038 .P
meillo@93	1039 Rose and Romine counted 24 visible and 9 more hidden switches for
meillo@93	1040 .Pn send .
meillo@97	1041 In nmh, they increased up to 32 visible and 12 hidden ones.
meillo@97	1042 At the time of writing, no more than 7 visible switches and 1 hidden switch
meillo@97	1043 have remained in mmh's
meillo@97	1044 .Pn send .
meillo@97	1045 (These numbers include two generic switches, help and version.)
meillo@93	1046 .P
meillo@97	1047 Fig. XXX
meillo@93	1048 .\" XXX Ref
meillo@97	1049 displays the number of switches for each of the tools that is available
meillo@97	1050 in both, nmh and mmh.
meillo@100	1051 The tools are sorted by the number of switches they had in nmh.
meillo@100	1052 Visible and hidden switches were counted,
meillo@97	1053 but not the generic help and version switches.
meillo@93	1054 Whereas in the beginning of the project, the average tool had 11 switches,
meillo@93	1055 now it has no more than 5 \(en only half as many.
meillo@93	1056 If the `no' switches and similar inverse variant are folded onto
meillo@100	1057 their counter-parts, the average tool had 8 switches in pre-mmh times and
meillo@100	1058 has 4 now.
meillo@93	1059 The total number of functional switches in mmh dropped from 465
meillo@93	1060 to 234.
meillo@58	1061
meillo@93	1062 .KS
meillo@93	1063 .in 1c
meillo@93	1064 .so input/switches.grap
meillo@93	1065 .KE
meillo@58	1066
meillo@93	1067 .P
meillo@93	1068 A part of the switches vanished after functions were removed.
meillo@93	1069 This was the case for network mail transfer, for instance.
meillo@97	1070 Sometimes, however, the work flow was the other way:
meillo@97	1071 I looked through the
meillo@97	1072 .Mp mh-chart (7)
meillo@97	1073 man page to identify the tools with apparently too many switches.
meillo@97	1074 Then considering the value of each of the switches by examining
meillo@97	1075 the tool's man page and source code, aided by recherche and testing.
meillo@97	1076 This way, the removal of functions was suggested by the aim to reduce
meillo@97	1077 the number of switches per command.
meillo@97	1078
meillo@58	1079
meillo@93	1080 .U3 "Draft Folder Facility
meillo@93	1081 .P
meillo@100	1082 A change early in the project was the complete transition from
meillo@93	1083 the single draft message to the draft folder facility.
meillo@97	1084 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@109	1085 The draft folder facility was introduced in the mid-eighties, when
meillo@100	1086 Rose and Romine called it a ``relatively new feature''.
meillo@93	1087 .[
meillo@93	1088 rose romine real work
meillo@93	1089 .]
meillo@110	1090 Since then, the facility had existed but was inactive by default.
meillo@93	1091 The default activation and the related rework of the tools made it
meillo@93	1092 possible to remove the
meillo@93	1093 .Sw -[no]draftfolder ,
meillo@93	1094 and
meillo@93	1095 .Sw -draftmessage
meillo@93	1096 switches from
meillo@93	1097 .Pn comp ,
meillo@93	1098 .Pn repl ,
meillo@93	1099 .Pn forw ,
meillo@93	1100 .Pn dist ,
meillo@93	1101 .Pn whatnow ,
meillo@93	1102 and
meillo@93	1103 .Pn send .
meillo@97	1104 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@97	1105 The only flexibility removed with this change is having multiple
meillo@97	1106 draft folders within one profile.
meillo@97	1107 I consider this a theoretical problem only.
meillo@93	1108 In the same go, the
meillo@93	1109 .Sw -draft
meillo@93	1110 switch of
meillo@93	1111 .Pn anno ,
meillo@93	1112 .Pn refile ,
meillo@93	1113 and
meillo@93	1114 .Pn send
meillo@93	1115 was removed.
meillo@93	1116 The special-casing of `the' draft message became irrelevant after
meillo@93	1117 the rework of the draft system.
meillo@93	1118 (See Sec. XXX.)
meillo@95	1119 Equally,
meillo@95	1120 .Pn comp
meillo@95	1121 lost its
meillo@95	1122 .Sw -file
meillo@95	1123 switch.
meillo@95	1124 The draft folder facility, together with the
meillo@95	1125 .Sw -form
meillo@95	1126 switch, are sufficient.
meillo@93	1127
meillo@95	1128
meillo@102	1129 .U3 "In Place Editing
meillo@93	1130 .P
meillo@93	1131 .Pn anno
meillo@93	1132 had the switches
meillo@93	1133 .Sw -[no]inplace
meillo@100	1134 to either annotate the message in place and thus preserve hard links,
meillo@93	1135 or annotate a copy to replace the original message, breaking hard links.
meillo@97	1136 Following the assumption that linked messages should truly be the
meillo@97	1137 same message, and annotating it should not break the link, the
meillo@93	1138 .Sw -[no]inplace
meillo@93	1139 switches were removed and the previous default
meillo@93	1140 .Sw -inplace
meillo@93	1141 was made the only behavior.
meillo@97	1142 .Ci c8195849d2e366c569271abb0f5f60f4ebf0b4d0
meillo@93	1143 The
meillo@93	1144 .Sw -[no]inplace
meillo@93	1145 switches of
meillo@93	1146 .Pn repl ,
meillo@93	1147 .Pn forw ,
meillo@93	1148 and
meillo@93	1149 .Pn dist
meillo@93	1150 could be removed, too, as they were simply passed through to
meillo@93	1151 .Pn anno .
meillo@93	1152 .P
meillo@93	1153 .Pn burst
meillo@93	1154 also had
meillo@93	1155 .Sw -[no]inplace
meillo@95	1156 switches, but with different meaning.
meillo@95	1157 With
meillo@95	1158 .Sw -inplace ,
meillo@95	1159 the digest had been replaced by the table of contents (i.e. the
meillo@110	1160 introduction text) and the burst messages were placed right
meillo@95	1161 after this message, renumbering all following messages.
meillo@95	1162 Also, any trailing text of the digest was lost, though,
meillo@95	1163 in practice, it usually consists of an end-of-digest marker only.
meillo@95	1164 Nontheless, this behavior appeared less elegant than the
meillo@95	1165 .Sw -noinplace
meillo@95	1166 behavior, which already had been the default.
meillo@95	1167 Nmh's
meillo@95	1168 .Mp burst (1)
meillo@95	1169 man page reads:
meillo@95	1170 .sp \n(PDu
meillo@98	1171 .QS
meillo@93	1172 If -noinplace is given, each digest is preserved, no table
meillo@93	1173 of contents is produced, and the messages contained within
meillo@93	1174 the digest are placed at the end of the folder. Other messages
meillo@93	1175 are not tampered with in any way.
meillo@98	1176 .QE
meillo@95	1177 .LP
meillo@93	1178 The decision to drop the
meillo@93	1179 .Sw -inplace
meillo@95	1180 behavior was supported by the code complexity and the possible data loss
meillo@95	1181 it caused.
meillo@93	1182 .Sw -noinplace
meillo@95	1183 was chosen to be the definitive behavior.
meillo@97	1184 .Ci 68a686adeb39223a5e1ad35e4a24890ec053679d
meillo@93	1185
meillo@95	1186
meillo@95	1187 .U3 "Forms and Format Strings
meillo@93	1188 .P
meillo@95	1189 Historically, the tools that had
meillo@95	1190 .Sw -form
meillo@95	1191 switches to supply a form file had
meillo@95	1192 .Sw -format
meillo@95	1193 switches as well to supply the contents of a form file as a string
meillo@95	1194 on the command line directly.
meillo@95	1195 In consequence, the following two lines equaled:
meillo@95	1196 .VS
meillo@95	1197 scan -form scan.mailx
meillo@95	1198 scan -format "`cat .../scan.mailx`"
meillo@95	1199 VE
meillo@95	1200 The
meillo@95	1201 .Sw -format
meillo@95	1202 switches were dropped in favor for extending the
meillo@95	1203 .Sw -form
meillo@95	1204 switches.
meillo@97	1205 .Ci f51956be123db66b00138f80464d06f030dbb88d
meillo@95	1206 If their argument starts with an equal sign (`='),
meillo@95	1207 then the rest of the argument is taken as a format string,
meillo@95	1208 otherwise the arguments is treated as the name of a format file.
meillo@95	1209 Thus, now the following two lines equal:
meillo@95	1210 .VS
meillo@95	1211 scan -form scan.mailx
meillo@95	1212 scan -form "=`cat .../scan.mailx`"
meillo@95	1213 VE
meillo@95	1214 This rework removed the prefix collision between
meillo@95	1215 .Sw -form
meillo@95	1216 and
meillo@95	1217 .Sw -format .
meillo@95	1218 Now, typing
meillo@95	1219 .Sw -fo
meillo@95	1220 suffices to specify form or format string.
meillo@95	1221 .P
meillo@95	1222 The different meaning of
meillo@95	1223 .Sw -format
meillo@95	1224 for
meillo@95	1225 .Pn repl
meillo@95	1226 and
meillo@95	1227 .Pn forw
meillo@95	1228 was removed in mmh.
meillo@95	1229 .Pn forw
meillo@95	1230 was completely switched to MIME-type forwarding, thus removing the
meillo@95	1231 .Sw -[no]format .
meillo@97	1232 .Ci 6e271608b7b9c23771523f88d23a4d3593010cf1
meillo@95	1233 For
meillo@95	1234 .Pn repl ,
meillo@95	1235 the
meillo@95	1236 .Sw -[no]format
meillo@95	1237 switches were reworked to
meillo@95	1238 .Sw -[no]filter
meillo@95	1239 switches.
meillo@97	1240 .Ci 67411b1f95d6ec987b4c732459e1ba8a8ac192c6
meillo@95	1241 The
meillo@95	1242 .Sw -format
meillo@95	1243 switches of
meillo@95	1244 .Pn send
meillo@95	1245 and
meillo@95	1246 .Pn post ,
meillo@95	1247 which had a third meaning,
meillo@95	1248 were removed likewise.
meillo@97	1249 .Ci f3cb7cde0e6f10451b6848678d95860d512224b9
meillo@95	1250 Eventually, the ambiguity of the
meillo@95	1251 .Sw -format
meillo@95	1252 switches was resolved by not anymore having any such switch in mmh.
meillo@95	1253
meillo@95	1254
meillo@95	1255 .U3 "MIME Tools
meillo@95	1256 .P
meillo@95	1257 The MIME tools, which were once part of
meillo@100	1258 .Pn mhn
meillo@100	1259 [sic!],
meillo@95	1260 had several switches that added little practical value to the programs.
meillo@95	1261 The
meillo@95	1262 .Sw -[no]realsize
meillo@95	1263 switches of
meillo@95	1264 .Pn mhbuild
meillo@95	1265 and
meillo@95	1266 .Pn mhlist
meillo@97	1267 were removed, doing real size calculations always now
meillo@97	1268 .Ci 8d8f1c3abc586c005c904e52c4adbfe694d2201c ,
meillo@97	1269 as
meillo@95	1270 ``This provides an accurate count at the expense of a small delay.''
meillo@95	1271 This small delay is not noticable on modern systems.
meillo@95	1272 .P
meillo@95	1273 The
meillo@95	1274 .Sw -[no]check
meillo@95	1275 switches were removed together with the support for
meillo@95	1276 .Hd Content-MD5
meillo@95	1277 header fields.
meillo@95	1278 .[
meillo@95	1279 rfc 1864
meillo@95	1280 .]
meillo@97	1281 .Ci 31dc797eb5178970d68962ca8939da3fd9a8efda
meillo@95	1282 (See Sec. XXX)
meillo@95	1283 .P
meillo@95	1284 The
meillo@95	1285 .Sw -[no]ebcdicsafe
meillo@95	1286 and
meillo@95	1287 .Sw -[no]rfc934mode
meillo@95	1288 switches of
meillo@95	1289 .Pn mhbuild
meillo@95	1290 were removed because they are considered obsolete.
meillo@97	1291 .Ci 01a3480928da485b4d6109d36d751dfa71799d58
meillo@97	1292 .Ci 3363e2624dce0eb8164cf8b3f1ab385c8ff72e88
meillo@95	1293 .P
meillo@95	1294 Content caching of external MIME parts, activated with the
meillo@95	1295 .Sw -rcache
meillo@95	1296 and
meillo@95	1297 .Sw -wcache
meillo@95	1298 switches was completely removed.
meillo@97	1299 .Ci d1fefd9f614e4dc3cda16da6c69133c1b2005269
meillo@97	1300 External MIME parts are rare today, having a caching facility
meillo@96	1301 for them is appears to be unnecessary.
meillo@95	1302 .P
meillo@95	1303 In pre-MIME times,
meillo@95	1304 .Pn mhl
meillo@95	1305 had covered many tasks that are part of MIME handling today.
meillo@95	1306 Therefore,
meillo@95	1307 .Pn mhl
meillo@95	1308 could be simplified to a large extend, reducing the number of its
meillo@95	1309 switches from 21 to 6.
meillo@97	1310 .Ci 350ad6d3542a07639213cf2a4fe524e829c1e7b6
meillo@97	1311 .Ci 0e46503be3c855bddaeae3843e1b659279c35d70
meillo@95	1312
meillo@95	1313
meillo@95	1314 .U3 "Mail Transfer Switches
meillo@95	1315 .P
meillo@95	1316 With the removal of the mail transfer facilities, a lot of switches
meillo@95	1317 vanished automatically.
meillo@95	1318 .Pn inc
meillo@95	1319 lost 9 switches, namely
meillo@95	1320 .Sw -host ,
meillo@95	1321 .Sw -port ,
meillo@95	1322 .Sw -user ,
meillo@95	1323 .Sw -proxy ,
meillo@95	1324 .Sw -snoop ,
meillo@95	1325 .Sw -[no]pack ,
meillo@95	1326 as well as
meillo@95	1327 .Sw -sasl
meillo@95	1328 and
meillo@95	1329 .Sw -saslmech .
meillo@95	1330 .Pn send
meillo@95	1331 and
meillo@95	1332 .Pn post
meillo@95	1333 lost 11 switches each, namely
meillo@95	1334 .Sw -server ,
meillo@95	1335 .Sw -port ,
meillo@95	1336 .Sw -client ,
meillo@95	1337 .Sw -user ,
meillo@95	1338 .Sw -mail ,
meillo@95	1339 .Sw -saml ,
meillo@95	1340 .Sw -send ,
meillo@95	1341 .Sw -soml ,
meillo@95	1342 .Sw -snoop ,
meillo@95	1343 as well as
meillo@95	1344 .Sw -sasl ,
meillo@95	1345 .Sw -saslmech ,
meillo@95	1346 and
meillo@95	1347 .Sw -tls .
meillo@95	1348 .Pn send
meillo@95	1349 had the switches only to pass them further to
meillo@95	1350 .Pn post ,
meillo@95	1351 because the user would invoke
meillo@95	1352 .Pn post
meillo@95	1353 not directly, but through
meillo@95	1354 .Pn send .
meillo@95	1355 All these switches, except
meillo@95	1356 .Sw -snoop
meillo@95	1357 were usually defined as default switches in the user's profile,
meillo@95	1358 but hardly given in interactive usage.
meillo@95	1359 .P
meillo@95	1360 Of course, those switches did not really ``vanish'', but the configuration
meillo@95	1361 they did was handed over to external MSAs and MRAs.
meillo@95	1362 Instead of setting up the mail transfer in mmh, it is set up in
meillo@95	1363 external tools.
meillo@95	1364 Yet, this simplifies mmh.
meillo@95	1365 Specialized external tools will likely have simple configuration files.
meillo@95	1366 Hence, instead of having one complicated central configuration file,
meillo@95	1367 the configuration of each domain is separate.
meillo@95	1368 Although the user needs to learn to configure each of the tools,
meillo@95	1369 each configuration is likely much simpler.
meillo@95	1370
meillo@95	1371
meillo@95	1372 .U3 "Maildrop Formats
meillo@95	1373 .P
meillo@95	1374 With the removal of MMDF maildrop format support,
meillo@95	1375 .Pn packf
meillo@95	1376 and
meillo@95	1377 .Pn rcvpack
meillo@95	1378 no longer needed their
meillo@95	1379 .Sw -mbox
meillo@95	1380 and
meillo@95	1381 .Sw -mmdf
meillo@95	1382 switches.
meillo@95	1383 .Sw -mbox
meillo@95	1384 is the sole behavior now.
meillo@97	1385 .Ci 3916ab66ad5d183705ac12357621ea8661afd3c0
meillo@95	1386 In the same go,
meillo@95	1387 .Pn packf
meillo@97	1388 and
meillo@97	1389 .Pn rcvpack
meillo@97	1390 were reworked (see Sec. XXX) and their
meillo@95	1391 .Sw -file
meillo@95	1392 switch became unnecessary.
meillo@97	1393 .Ci ca1023716d4c2ab890696f3e41fa0d94267a940e
meillo@95	1394
meillo@95	1395
meillo@95	1396 .U3 "Terminal Magic
meillo@95	1397 .P
meillo@95	1398 Mmh's tools will no longer clear the screen (\c
meillo@95	1399 .Pn scan 's
meillo@95	1400 and
meillo@95	1401 .Pn mhl 's
meillo@95	1402 .Sw -[no]clear
meillo@97	1403 switches
meillo@97	1404 .Ci e57b17343dcb3ff373ef4dd089fbe778f0c7c270
meillo@97	1405 .Ci 943765e7ac5693ae177fd8d2b5a2440e53ce816e ).
meillo@95	1406 Neither will
meillo@95	1407 .Pn mhl
meillo@95	1408 ring the bell (\c
meillo@97	1409 .Sw -[no]bell
meillo@97	1410 .Ci e11983f44e59d8de236affa5b0d0d3067c192e24 )
meillo@95	1411 nor page the output itself (\c
meillo@97	1412 .Sw -length
meillo@97	1413 .Ci 5b9d883db0318ed2b84bb82dee880d7381f99188 ).
meillo@95	1414 .P
meillo@95	1415 Generally, the pager to use is no longer specified with the
meillo@95	1416 .Sw -[no]moreproc
meillo@95	1417 command line switches for
meillo@95	1418 .Pn mhl
meillo@95	1419 and
meillo@95	1420 .Pn show /\c
meillo@95	1421 .Pn mhshow .
meillo@97	1422 .Ci 39e87a75b5c2d3572ec72e717720b44af291e88a
meillo@95	1423 .P
meillo@95	1424 .Pn prompter
meillo@95	1425 lost its
meillo@95	1426 .Sw -erase
meillo@95	1427 and
meillo@95	1428 .Sw -kill
meillo@95	1429 switches because today the terminal cares for the line editing keys.
meillo@95	1430
meillo@95	1431
meillo@95	1432 .U3 "Header Printing
meillo@95	1433 .P
meillo@95	1434 .Pn folder 's
meillo@95	1435 data output is self-explaining enough that
meillo@95	1436 displaying the header line makes few sense.
meillo@95	1437 Hence, the
meillo@95	1438 .Sw -[no]header
meillo@95	1439 switch was removed and headers are never printed.
meillo@97	1440 .Ci 601cc73d1fa05ce96faa728f036d6c51b91701c7
meillo@95	1441 .P
meillo@95	1442 In
meillo@95	1443 .Pn mhlist ,
meillo@95	1444 the
meillo@95	1445 .Sw -[no]header
meillo@95	1446 switches were removed, too.
meillo@97	1447 .Ci b24f96523aaf60e44e04a3ffb1d22e69a13a602f
meillo@95	1448 But in this case headers are always printed,
meillo@95	1449 because the output is not self-explaining.
meillo@95	1450 .P
meillo@95	1451 .Pn scan
meillo@95	1452 also had
meillo@95	1453 .Sw -[no]header
meillo@95	1454 switches.
meillo@95	1455 Printing the header had been sensible until the introduction of
meillo@95	1456 format strings made it impossible to display the column headings.
meillo@95	1457 Only the folder name and the current date remained to be printed.
meillo@95	1458 As this information can be perfectly retrieved by
meillo@95	1459 .Pn folder
meillo@95	1460 and
meillo@95	1461 .Pn date ,
meillo@95	1462 consequently, the switches were removed.
meillo@97	1463 .Ci c477dc5d1d03fa6d9a8ab3dd3508c63cbddc044e
meillo@95	1464 .P
meillo@95	1465 By removing all
meillo@95	1466 .Sw -header
meillo@95	1467 switches, the collision with
meillo@95	1468 .Sw -help
meillo@95	1469 on the first two letters was resolved.
meillo@95	1470 Currently,
meillo@95	1471 .Sw -h
meillo@95	1472 evaluates to
meillo@95	1473 .Sw -help
meillo@95	1474 for all tools of mmh.
meillo@95	1475
meillo@95	1476
meillo@95	1477 .U3 "Suppressing Edits or the WhatNow Shell
meillo@95	1478 .P
meillo@95	1479 The
meillo@95	1480 .Sw -noedit
meillo@100	1481 switch of
meillo@95	1482 .Pn comp ,
meillo@95	1483 .Pn repl ,
meillo@95	1484 .Pn forw ,
meillo@95	1485 .Pn dist ,
meillo@95	1486 and
meillo@95	1487 .Pn whatnow
meillo@95	1488 was removed, but it can now be replaced by specifying
meillo@95	1489 .Sw -editor
meillo@95	1490 with an empty argument.
meillo@97	1491 .Ci 75fca31a5b9d5c1a99c74ab14c94438d8852fba9
meillo@95	1492 (Specifying
meillo@95	1493 .Cl "-editor true
meillo@95	1494 is nearly the same, only differing by the previous editor being set.)
meillo@95	1495 .P
meillo@95	1496 The more important change is the removal of the
meillo@95	1497 .Sw -nowhatnowproc
meillo@95	1498 switch.
meillo@97	1499 .Ci ee4f43cf2ef0084ec698e4e87159a94c01940622
meillo@95	1500 This switch had introduced an awkward behavior, as explained in nmh's
meillo@95	1501 man page for
meillo@95	1502 .Mp comp (1):
meillo@98	1503 .QS
meillo@98	1504 The \-editor editor switch indicates the editor to use for
meillo@98	1505 the initial edit. Upon exiting from the editor, comp will
meillo@98	1506 invoke the whatnow program. See whatnow(1) for a discussion
meillo@98	1507 of available options. The invocation of this program can be
meillo@98	1508 inhibited by using the \-nowhatnowproc switch. (In truth of
meillo@98	1509 fact, it is the whatnow program which starts the initial
meillo@98	1510 edit. Hence, \-nowhatnowproc will prevent any edit from
meillo@95	1511 occurring.)
meillo@98	1512 .QE
meillo@95	1513 .P
meillo@95	1514 Effectively, the
meillo@95	1515 .Sw -nowhatnowproc
meillo@100	1516 switch creates only a draft message.
meillo@95	1517 As
meillo@95	1518 .Cl "-whatnowproc true
meillo@95	1519 causes the same behavior, the
meillo@95	1520 .Sw -nowhatnowproc
meillo@95	1521 switch was removed for being redundant.
meillo@100	1522 Likely, the
meillo@95	1523 .Sw -nowhatnowproc
meillo@100	1524 switch was intended to be used by front-ends.
meillo@95	1525
meillo@95	1526
meillo@95	1527 .U3 "Compatibility Switches
meillo@95	1528 .BU
meillo@95	1529 The hidden
meillo@95	1530 .Sw -[no]total
meillo@95	1531 switches of
meillo@95	1532 .Pn flist .
meillo@95	1533 They were simply the inverse of the visible
meillo@95	1534 .Sw -[no]fast
meillo@95	1535 switches:
meillo@95	1536 .Sw -total
meillo@95	1537 was
meillo@95	1538 .Sw -nofast
meillo@95	1539 and
meillo@95	1540 .Sw -nototal
meillo@95	1541 was
meillo@95	1542 .Sw -fast .
meillo@95	1543 I removed the
meillo@95	1544 .Sw -[no]total
meillo@95	1545 legacy.
meillo@97	1546 .Ci ea21fe2c4bd23c639bef251398fae809875732ec
meillo@95	1547 .BU
meillo@95	1548 The
meillo@95	1549 .Sw -subject
meillo@95	1550 switch of
meillo@95	1551 .Pn sortm
meillo@95	1552 existed for compatibility only.
meillo@95	1553 It can be fully replaced by
meillo@95	1554 .Cl "-textfield subject
meillo@95	1555 thus it was removed.
meillo@97	1556 .Ci 00140a3c86e9def69d98ba2ffd4d6e50ef6326ea
meillo@95	1557
meillo@95	1558
meillo@95	1559 .U3 "Various
meillo@95	1560 .BU
meillo@96	1561 In order to avoid prefix collisions among switch names, the
meillo@95	1562 .Sw -version
meillo@95	1563 switch was renamed to
meillo@95	1564 .Sw -Version
meillo@95	1565 (with capital `V').
meillo@97	1566 .Ci 32b2354dbaf4bf934936eb5b102a4a3d2fdd209a
meillo@95	1567 Every program has the
meillo@95	1568 .Sw -version
meillo@95	1569 switch but its first three letters collided with the
meillo@95	1570 .Sw -verbose
meillo@95	1571 switch, present in many programs.
meillo@95	1572 The rename solved this problem once for all.
meillo@95	1573 Although this rename breaks a basic interface, having the
meillo@95	1574 .Sw -V
meillo@95	1575 abbreviation to display the version information, isn't all too bad.
meillo@95	1576 .BU
meillo@95	1577 .Sw -[no]preserve
meillo@95	1578 of
meillo@95	1579 .Pn refile
meillo@95	1580 was removed because what use was it anyway?
meillo@98	1581 .QS
meillo@95	1582 Normally when a message is refiled, for each destination
meillo@95	1583 folder it is assigned the number which is one above the current
meillo@95	1584 highest message number in that folder. Use of the
meillo@95	1585 \-preserv [sic!] switch will override this message renaming, and try
meillo@95	1586 to preserve the number of the message. If a conflict for a
meillo@95	1587 particular folder occurs when using the \-preserve switch,
meillo@95	1588 then refile will use the next available message number which
meillo@95	1589 is above the message number you wish to preserve.
meillo@98	1590 .QE
meillo@95	1591 .BU
meillo@95	1592 The removal of the
meillo@95	1593 .Sw -[no]reverse
meillo@95	1594 switches of
meillo@95	1595 .Pn scan
meillo@97	1596 .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@95	1597 is a bug fix, supported by the comments
meillo@95	1598 ``\-[no]reverse under #ifdef BERK (I really HATE this)''
meillo@95	1599 by Rose and
meillo@95	1600 ``Lists messages in reverse order with the `\-reverse' switch.
meillo@95	1601 This should be considered a bug.'' by Romine in the documentation.
meillo@97	1602 The question remains why neither Rose and Romine had fixed this
meillo@109	1603 bug in the eighties when they wrote these comments nor has anyone
meillo@95	1604 thereafter.
meillo@93	1605
meillo@93	1606
meillo@93	1607 .ig
meillo@93	1608
meillo@95	1609 forw: [no]dashstuffing(mhl)
meillo@93	1610
meillo@95	1611 mhshow: [no]pause [no]serialonly
meillo@93	1612
meillo@93	1613 mhmail: resent queued
meillo@93	1614 inc: snoop, (pop)
meillo@93	1615
meillo@95	1616 mhl: [no]faceproc folder sleep
meillo@95	1617 [no]dashstuffing(forw) digest list volume number issue number
meillo@93	1618
meillo@95	1619 prompter: [no]doteof
meillo@93	1620
meillo@93	1621 refile: [no]preserve [no]unlink [no]rmmproc
meillo@93	1622
meillo@95	1623 send: [no]forward [no]mime [no]msgid
meillo@93	1624 [no]push split [no]unique (sasl) width snoop [no]dashstuffing
meillo@93	1625 attach attachformat
meillo@93	1626 whatnow: (noedit) attach
meillo@93	1627
meillo@93	1628 slocal: [no]suppressdups
meillo@93	1629
meillo@95	1630 spost: [no]filter [no]backup width [no]push idanno
meillo@93	1631 [no]check(whom) whom(whom)
meillo@93	1632
meillo@93	1633 whom: ???
meillo@93	1634
meillo@95	1635 ..
meillo@93	1636
meillo@93	1637
meillo@93	1638 .ig
meillo@93	1639
meillo@93	1640 .P
meillo@93	1641 In the best case, all switches are unambiguous on the first character,
meillo@93	1642 or on the three-letter prefix for the `no' variants.
meillo@96	1643 Reducing switch prefix collisions, shortens the necessary prefix length
meillo@93	1644 the user must type.
meillo@93	1645 Having less switches helps best.
meillo@93	1646
meillo@93	1647 ..
meillo@58	1648
meillo@95	1649
meillo@102	1650 .\" XXX: whatnow prompt commands
meillo@102	1651
meillo@102	1652
meillo@95	1653
meillo@95	1654
meillo@133	1655 .\" --------------------------------------------------------------
meillo@74	1656 .H1 "Modernizing
meillo@102	1657 .P
meillo@118	1658 In the over thirty years of MH's existence, its code base was
meillo@118	1659 extended more and more.
meillo@118	1660 New features entered the project and became alternatives to the
meillo@118	1661 existing behavior.
meillo@118	1662 Relicts from several decades have gathered in the code base,
meillo@118	1663 but seldom obsolete features were dropped.
meillo@118	1664 This section describes the removing of old code
meillo@118	1665 and the modernizing of the default setup.
meillo@118	1666 It focuses on the functional aspect only;
meillo@118	1667 the non-functional aspects of code style are discussed in
meillo@118	1668 .\" FIXME REF
meillo@118	1669 Sec. XXX.
meillo@58	1670
meillo@58	1671
meillo@100	1672 .H2 "Code Relicts
meillo@0	1673 .P
meillo@109	1674 My position to drop obsolete functions of mmh, in order to remove old code,
meillo@104	1675 is much more revolutional than the nmh community likes to have it.
meillo@104	1676 Working on an experimental version, I was able to quickly drop
meillo@104	1677 functionality I considered ancient.
meillo@104	1678 The need for consensus with peers would have slowed this process down.
meillo@104	1679 Without the need to justify my decisions, I was able to rush forward.
meillo@110	1680 In December 2011, Paul Vixie motivated the nmh developers to just
meillo@104	1681 do the work:
meillo@104	1682 .[
meillo@104	1683 paul vixie edginess nmh-workers
meillo@104	1684 .]
meillo@104	1685 .QS
meillo@104	1686 let's stop walking on egg shells with this code base. there's no need to
meillo@104	1687 discuss whether to keep using vfork, just note in [sic!] passing, [...]
meillo@104	1688 we don't need a separate branch for removing vmh
meillo@104	1689 or ridding ourselves of #ifdef's or removing posix replacement functions
meillo@104	1690 or depending on pure ansi/posix "libc".
meillo@104	1691 .QP
meillo@104	1692 these things should each be a day or two of work and the "main branch"
meillo@104	1693 should just be modern. [...]
meillo@104	1694 let's push forward, aggressively.
meillo@104	1695 .QE
meillo@104	1696 .LP
meillo@104	1697 I did so already in the months before.
meillo@104	1698 I pushed forward.
meillo@104	1699 I simply dropped the cruft.
meillo@104	1700 .P
meillo@104	1701 The decision to drop a feature was based on literature research and
meillo@104	1702 careful thinking, but whether having had contact to this particular
meillo@104	1703 feature within my own computer life served as a rule of thumb.
meillo@109	1704 Always, I explained my reasons in the commit messages
meillo@109	1705 in the version control system.
meillo@104	1706 Hence, others can comprehend my view and argue for undoing the change
meillo@104	1707 if I have missed an important aspect.
meillo@109	1708 I was quick in dropping parts.
meillo@109	1709 I rather re-included falsely dropped parts than going a slower pace.
meillo@109	1710 Mmh is experimental work; it required tough decisions.
meillo@12	1711
meillo@102	1712
meillo@104	1713 .U3 "Forking
meillo@12	1714 .P
meillo@109	1715 Being a tool chest, MH creates many processes.
meillo@104	1716 In earlier times
meillo@104	1717 .Fu fork()
meillo@104	1718 had been an expensive system call, because the process's image needed
meillo@104	1719 to be duplicated completely at once.
meillo@109	1720 This was especially painful in the common case when the image gets
meillo@104	1721 replaced by a call to
meillo@104	1722 .Fu exec()
meillo@104	1723 right after having forked the child process.
meillo@104	1724 The
meillo@104	1725 .Fu vfork()
meillo@104	1726 system call was invented to speed up this particular case.
meillo@104	1727 It completely omits the duplication of the image.
meillo@104	1728 On old systems this resulted in significant speed ups.
meillo@104	1729 Therefore MH used
meillo@104	1730 .Fu vfork()
meillo@104	1731 whenever possible.
meillo@12	1732 .P
meillo@104	1733 Modern memory management units support copy-on-write semantics, which make
meillo@104	1734 .Fu fork()
meillo@104	1735 almost as fast as
meillo@104	1736 .Fu vfork() .
meillo@104	1737 The man page of
meillo@104	1738 .Mp vfork (2)
meillo@104	1739 in FreeBSD 8.0 states:
meillo@104	1740 .QS
meillo@104	1741 This system call will be eliminated when proper system sharing mechanisms
meillo@104	1742 are implemented. Users should not depend on the memory sharing semantics
meillo@104	1743 of vfork() as it will, in that case, be made synonymous to fork(2).
meillo@104	1744 .QE
meillo@104	1745 .LP
meillo@104	1746 Vixie supports the removal with the note that ``the last
meillo@104	1747 system on which fork was so slow that an mh user would notice it, was
meillo@104	1748 Eunice. that was 1987''.
meillo@104	1749 .[
meillo@104	1750 nmh-workers vixie edginess
meillo@104	1751 .]
meillo@104	1752 I replaced all calls to
meillo@104	1753 .Fu vfork()
meillo@104	1754 with calls to
meillo@104	1755 .Fu fork() .
meillo@109	1756 .Ci 40821f5c1316e9205a08375e7075909cc9968e7d
meillo@104	1757 .P
meillo@104	1758 Related to the costs of
meillo@104	1759 .Fu fork()
meillo@104	1760 is the probability of its success.
meillo@109	1761 In the eighties, on heavy loaded systems, calls to
meillo@104	1762 .Fu fork()
meillo@104	1763 were prone to failure.
meillo@104	1764 Hence, many of the
meillo@104	1765 .Fu fork()
meillo@104	1766 calls in the code were wrapped into loops to retry the
meillo@104	1767 .Fu fork()
meillo@109	1768 several times, to increase the changes to succeed, eventually.
meillo@109	1769 On modern systems, a failing
meillo@104	1770 .Fu fork()
meillo@109	1771 call is unusual.
meillo@104	1772 Hence, in the rare case when
meillo@104	1773 .Fu fork()
meillo@104	1774 fails, mmh programs simply abort.
meillo@109	1775 .Ci 5fbf37ee68e018998ada61eeab73e035b26834b6
meillo@12	1776
meillo@12	1777
meillo@109	1778 .U3 "Header Fields
meillo@104	1779 .BU
meillo@84	1780 The
meillo@84	1781 .Hd Encrypted
meillo@104	1782 header field was introduced by RFC\\|822,
meillo@109	1783 but already marked as legacy in RFC\\|2822.
meillo@109	1784 Today, OpenPGP provides the basis for standardized exchange of encrypted
meillo@104	1785 messages [RFC\\|4880, RFC\\|3156].
meillo@109	1786 Hence, the support for
meillo@104	1787 .Hd Encrypted
meillo@104	1788 header fields is removed in mmh.
meillo@109	1789 .Ci 064527f7b57ab050e5af13e15ad99aeeab125857
meillo@104	1790 .BU
meillo@84	1791 Native support for
meillo@84	1792 .Hd Face
meillo@104	1793 header fields has been removed, as well.
meillo@109	1794 .Ci 8e5be81f784682822f5e868c1bf3c8624682bd23
meillo@104	1795 This feature is similar to the
meillo@84	1796 .Hd X-Face
meillo@84	1797 header field in its intent,
meillo@21	1798 but takes a different approach to store the image.
meillo@84	1799 Instead of encoding the image data directly into the header field,
meillo@109	1800 it contains the hostname and UDP port where the image
meillo@109	1801 date can be retrieved.
meillo@109	1802 There exists even a third Face system,
meillo@109	1803 which is the successor of
meillo@109	1804 .Hd X-Face ,
meillo@109	1805 although it re-uses the
meillo@104	1806 .Hd Face
meillo@109	1807 header field.
meillo@109	1808 It was invented in 2005 and supports colored PNG images.
meillo@104	1809 None of the Face systems described here is popular today.
meillo@104	1810 Hence, mmh has no direct support for them.
meillo@104	1811 .BU
meillo@104	1812 The
meillo@104	1813 .Hd Content-MD5
meillo@104	1814 header field was introduced by RFC\\|1864.
meillo@104	1815 It provides detection of data corruption during the transfer.
meillo@104	1816 But it can not ensure verbatim end-to-end delivery of the contents
meillo@104	1817 [RFC\\|1864].
meillo@104	1818 The proper approach to verify content integrity in an
meillo@104	1819 end-to-end relationship is the use of digital cryptography.
meillo@104	1820 .\" XXX (RFCs FIXME).
meillo@104	1821 On the other hand, transfer protocols should detect corruption during
meillo@109	1822 the transmission.
meillo@109	1823 The TCP includes a checksum field therefore.
meillo@104	1824 These two approaches in combinations render the
meillo@104	1825 .Hd Content-MD5
meillo@104	1826 header field superfluous.
meillo@109	1827 Not a single one out of 4\\|200 messages from two decades
meillo@109	1828 in an nmh-workers mailing list archive contains a
meillo@104	1829 .Hd Content-MD5
meillo@104	1830 header field.
meillo@104	1831 Neither did any of the 60\\|000 messages in my personal mail storage.
meillo@104	1832 Removing the support for this header field,
meillo@104	1833 removed the last place where MD5 computation was needed.
meillo@109	1834 .Ci 31dc797eb5178970d68962ca8939da3fd9a8efda
meillo@104	1835 Hence, the MD5 code could be removed as well.
meillo@104	1836 Over 500 lines of code vanished by this one change.
meillo@104	1837
meillo@104	1838
meillo@104	1839 .U3 "MMDF maildrop support
meillo@21	1840 .P
meillo@104	1841 This type of format is conceptionally similar to the mbox format,
meillo@104	1842 but uses a different message delimiter (`\fL^A^A^A^A\fP' instead of
meillo@104	1843 `\fLFrom\0\fP').
meillo@104	1844 Mbox is the de-facto standard maildrop format on Unix,
meillo@109	1845 whereas the MMDF maildrop format became forgotten.
meillo@104	1846 I did drop MMDF maildrop format support.
meillo@109	1847 Mbox is the only packed mailbox format supported in mmh.
meillo@104	1848 .P
meillo@109	1849 The simplifications within the code were moderate.
meillo@109	1850 Mainly, the reading and writing of MMDF mailbox files was removed.
meillo@109	1851 But also, switches of
meillo@109	1852 .Pn packf
meillo@104	1853 and
meillo@109	1854 .Pn rcvpack
meillo@109	1855 could be removed.
meillo@109	1856 .Ci 3916ab66ad5d183705ac12357621ea8661afd3c0
meillo@109	1857 In the message parsing function
meillo@109	1858 .Fn sbr/m_getfld.c ,
meillo@109	1859 knowledge of MMDF packed mail boxes was removed.
meillo@109	1860 .Ci 684ec30d81e1223a282764452f4902ed4ad1c754
meillo@109	1861 Further code structure simplifications may be possible there,
meillo@109	1862 because only one single packed mailbox format is left to be supported.
meillo@104	1863 I have not worked on them yet because
meillo@104	1864 .Fu m_getfld()
meillo@104	1865 is heavily optimized and thus dangerous to touch.
meillo@104	1866 The risk of damaging the intricate workings of the optimized code is
meillo@104	1867 too high.
meillo@104	1868 .\" XXX: move somewhere else
meillo@104	1869 This problem is know to the developers of nmh, too.
meillo@109	1870 They also avoid touching this minefield.
meillo@104	1871
meillo@12	1872
meillo@101	1873 .U3 "Prompter's Control Keys
meillo@20	1874 .P
meillo@20	1875 The program
meillo@20	1876 .Pn prompter
meillo@104	1877 queries the user to fill in a message form.
meillo@104	1878 When used by
meillo@20	1879 .Pn comp
meillo@104	1880 as
meillo@104	1881 .Cl "comp -editor prompter" ,
meillo@20	1882 the resulting behavior is similar to
meillo@20	1883 .Pn mailx .
meillo@51	1884 Apparently,
meillo@20	1885 .Pn prompter
meillo@104	1886 hadn't been touched lately.
meillo@104	1887 Otherwise it's hardly explainable why it
meillo@20	1888 still offered the switches
meillo@84	1889 .Sw -erase
meillo@84	1890 .Ar chr
meillo@20	1891 and
meillo@84	1892 .Sw -kill
meillo@84	1893 .Ar chr
meillo@20	1894 to name the characters for command line editing.
meillo@21	1895 The times when this had been necessary are long time gone.
meillo@20	1896 Today these things work out-of-the-box, and if not, are configured
meillo@20	1897 with the standard tool
meillo@20	1898 .Pn stty .
meillo@104	1899 The switches are removed now
meillo@104	1900 .Ci 0bd9750710cdbab80cfb4036dd87af20afe1552f .
meillo@20	1901
meillo@104	1902
meillo@109	1903 .U3 "Hardcopy Terminal Support
meillo@21	1904 .P
meillo@109	1905 More of a funny anecdote is a check for being connected to a
meillo@109	1906 hardcopy terminal.
meillo@109	1907 It remained in the code until Spring 2012, when I finally removed it
meillo@104	1908 .Ci b7764c4a6b71d37918a97594d866258f154017ca .
meillo@109	1909 I would be truly happy to see such a terminal in action today,
meillo@109	1910 maybe even being able to work on it.
meillo@109	1911 But I fear my chances are null.
meillo@21	1912 .P
meillo@109	1913 The check only prevented a pager to be placed between the printing
meillo@104	1914 program (\c
meillo@104	1915 .Pn mhl )
meillo@104	1916 and the terminal.
meillo@109	1917 In nmh, this could have been ensured statically with the
meillo@104	1918 .Sw -nomoreproc
meillo@109	1919 at the command line, too.
meillo@121	1920 In mmh, setting the profile entry
meillo@104	1921 .Pe Pager
meillo@104	1922 or the environment variable
meillo@104	1923 .Ev PAGER
meillo@104	1924 to
meillo@109	1925 .Pn cat
meillo@109	1926 does the job.
meillo@104	1927
meillo@104	1928
meillo@21	1929
meillo@12	1930
meillo@58	1931 .H2 "Attachments
meillo@22	1932 .P
meillo@101	1933 The mind model of email attachments is unrelated to MIME.
meillo@101	1934 Although the MIME RFCs (2045 through 2049) define the technical
meillo@109	1935 requirements for having attachments, they do not mention the word
meillo@101	1936 ``attachment''.
meillo@101	1937 Instead of attachments, MIME talks about ``multi-part message bodies''
meillo@101	1938 [RFC\\|2045], a more general concept.
meillo@101	1939 Multi-part messages are messages
meillo@101	1940 ``in which one or more different
meillo@101	1941 sets of data are combined in a single body''
meillo@101	1942 [RFC\\|2046].
meillo@101	1943 MIME keeps its descriptions generic;
meillo@101	1944 it does not imply specific usage models.
meillo@109	1945 One usage model became prevalent: attachments.
meillo@101	1946 The idea is having a main text document with files of arbitrary kind
meillo@101	1947 attached to it.
meillo@101	1948 In MIME terms, this is a multi-part message having a text part first
meillo@110	1949 and parts of arbitrary type following.
meillo@101	1950 .P
meillo@101	1951 MH's MIME support is a direct implementation of the RFCs.
meillo@101	1952 The perception of the topic described in the RFCs is clearly visible
meillo@101	1953 in MH's implementation.
meillo@109	1954 In result, MH had all the MIME features but no idea of attachments.
meillo@109	1955 But users don't need all the MIME features,
meillo@109	1956 they want convenient attachment handling.
meillo@109	1957
meillo@102	1958
meillo@102	1959 .U3 "Composing MIME Messages
meillo@102	1960 .P
meillo@102	1961 In order to improve the situation on the message composing side,
meillo@102	1962 Jon Steinhart had added an attachment system to nmh in 2002.
meillo@101	1963 .Ci 7480dbc14bc90f2d872d434205c0784704213252
meillo@102	1964 In the file
meillo@102	1965 .Fn docs/README-ATTACHMENTS ,
meillo@102	1966 he described his motivation to do so as such:
meillo@101	1967 .QS
meillo@101	1968 Although nmh contains the necessary functionality for MIME message handing,
meillo@101	1969 the interface to this functionality is pretty obtuse.
meillo@101	1970 There's no way that I'm ever going to convince my partner to write
meillo@101	1971 .Pn mhbuild
meillo@101	1972 composition files!
meillo@101	1973 .QE
meillo@102	1974 .LP
meillo@102	1975 With this change, the mind model of attachments entered nmh.
meillo@102	1976 In the same document:
meillo@101	1977 .QS
meillo@101	1978 These changes simplify the task of managing attachments on draft files.
meillo@101	1979 They allow attachments to be added, listed, and deleted.
meillo@101	1980 MIME messages are automatically created when drafts with attachments
meillo@101	1981 are sent.
meillo@101	1982 .QE
meillo@102	1983 .LP
meillo@102	1984 Unfortunately, the attachment system,
meillo@102	1985 like any new facilities in nmh,
meillo@110	1986 was inactive by default.
meillo@101	1987 .P
meillo@101	1988 During my work in Argentina, I tried to improve the attachment system.
meillo@102	1989 But, because of great opposition in the nmh community,
meillo@102	1990 my patch died as a proposal on the mailing list, after long discussions.
meillo@101	1991 .[
meillo@101	1992 nmh-workers attachment proposal
meillo@101	1993 .]
meillo@110	1994 In January 2012, I extended the patch and applied it to mmh.
meillo@101	1995 .Ci 8ff284ff9167eff8f5349481529332d59ed913b1
meillo@102	1996 In mmh, the attachment system is active by default.
meillo@102	1997 Instead of command line switches, the
meillo@102	1998 .Pe Attachment-Header
meillo@102	1999 profile entry is used to specify
meillo@102	2000 the name of the attachment header field.
meillo@102	2001 It is pre-defined to
meillo@102	2002 .Hd Attach .
meillo@101	2003 .P
meillo@101	2004 To add an attachment to a draft, simply add an attachment header:
meillo@101	2005 .VS
meillo@101	2006 To: bob
meillo@101	2007 Subject: The file you wanted
meillo@101	2008 Attach: /path/to/the/file-bob-wanted
meillo@101	2009 --------
meillo@101	2010 Here it is.
meillo@101	2011 VE
meillo@101	2012 The header field can be added to the draft manually in the editor,
meillo@102	2013 or by using the `attach' command at the WhatNow prompt, or
meillo@102	2014 non-interactively with
meillo@101	2015 .Pn anno :
meillo@101	2016 .VS
meillo@102	2017 anno -append -nodate -component Attach -text /path/to/attachment
meillo@101	2018 VE
meillo@102	2019 Drafts with attachment headers are converted to MIME automatically by
meillo@102	2020 .Pn send .
meillo@102	2021 The conversion to MIME is invisible to the user.
meillo@102	2022 The draft stored in the draft folder is always in source form, with
meillo@101	2023 attachment headers.
meillo@101	2024 If the MIMEification fails, for instance because the file to attach
meillo@101	2025 is not accessible, the original draft is not changed.
meillo@101	2026 .P
meillo@102	2027 The attachment system handles the forwarding of messages, too.
meillo@101	2028 If the attachment header value starts with a plus character (`+'),
meillo@101	2029 like in
meillo@101	2030 .Cl "Attach: +bob 30 42" ,
meillo@101	2031 The given messages in the specified folder will be attached.
meillo@101	2032 This allowed to simplify
meillo@101	2033 .Pn forw .
meillo@101	2034 .Ci f41f04cf4ceca7355232cf7413e59afafccc9550
meillo@101	2035 .P
meillo@101	2036 Closely related to attachments is non-ASCII text content,
meillo@101	2037 because it requires MIME too.
meillo@102	2038 In nmh, the user needed to call `mime' at the WhatNow prompt
meillo@101	2039 to have the draft converted to MIME.
meillo@102	2040 This was necessary whenever the draft contained non-ASCII characters.
meillo@101	2041 If the user did not call `mime', a broken message would be sent.
meillo@101	2042 Therefore, the
meillo@101	2043 .Pe automimeproc
meillo@101	2044 profile entry could be specified to have the `mime' command invoked
meillo@102	2045 automatically each time.
meillo@101	2046 Unfortunately, this approach conflicted with with attachment system
meillo@101	2047 because the draft would already be in MIME format at the time
meillo@101	2048 when the attachment system wanted to MIMEify it.
meillo@102	2049 To use nmh's attachment system, `mime' must not be called at the
meillo@102	2050 WhatNow prompt and
meillo@101	2051 .Pe automimeproc
meillo@102	2052 must not be set in the profile.
meillo@101	2053 But then the case of non-ASCII text without attachment headers was
meillo@101	2054 not caught.
meillo@102	2055 All in all, the solution was complex and irritating.
meillo@102	2056 My patch from December 2010 would have simplified the situation.
meillo@102	2057 .P
meillo@101	2058 Mmh's current solution is even more elaborate.
meillo@101	2059 Any necessary MIMEification is done automatically.
meillo@101	2060 There is no `mime' command at the WhatNow prompt anymore.
meillo@102	2061 The draft will be converted automatically to MIME when either an
meillo@102	2062 attachment header or non-ASCII text is present.
meillo@101	2063 Further more, the special meaning of the hash character (`#')
meillo@102	2064 at line beginnings in the draft message is removed.
meillo@102	2065 Users need not at all deal with the whole topic.
meillo@101	2066 .P
meillo@102	2067 Although the new approach does not anymore support arbitrary MIME
meillo@102	2068 compositions directly, the full power of
meillo@101	2069 .Pn mhbuild
meillo@101	2070 can still be accessed.
meillo@102	2071 Given no attachment headers are included, the user can create
meillo@101	2072 .Pn mhbuild
meillo@102	2073 composition drafts like in nmh.
meillo@101	2074 Then, at the WhatNow prompt, he needs to invoke
meillo@101	2075 .Cl "edit mhbuild
meillo@101	2076 to convert it to MIME.
meillo@110	2077 Because the resulting draft does neither contain non-ASCII characters
meillo@102	2078 nor has it attachment headers, the attachment system will not touch it.
meillo@101	2079 .P
meillo@121	2080 The approach taken in mmh is tailored towards todays most common case:
meillo@101	2081 a text part with possibly attachments.
meillo@102	2082 This case is simplified a lot for users.
meillo@102	2083
meillo@112	2084
meillo@102	2085 .U3 "MIME Type Guessing
meillo@102	2086 .P
meillo@102	2087 The use of
meillo@101	2088 .Pn mhbuild
meillo@102	2089 composition drafts had one notable advantage over attachment headers
meillo@102	2090 from the programmer's point of view: The user provides the appropriate
meillo@102	2091 MIME types for files to include.
meillo@102	2092 The attachment system needs to find out the correct MIME type itself.
meillo@102	2093 This is a difficult task, yet it spares the user irritating work.
meillo@102	2094 Determining the correct MIME type of content is partly mechanical,
meillo@102	2095 partly intelligent work.
meillo@102	2096 Forcing the user to find out the correct MIME type,
meillo@102	2097 forces him to do partly mechanical work.
meillo@102	2098 Letting the computer do the work, can lead to bad choices for difficult
meillo@102	2099 content.
meillo@102	2100 For mmh, the latter option was chosen.
meillo@102	2101 .P
meillo@102	2102 Determining the MIME type by the suffix of the file name is a dumb
meillo@102	2103 approach, yet it is simple to implement and provides good results
meillo@102	2104 for the common cases.
meillo@102	2105 Mmh implements this approach in the
meillo@102	2106 .Pn print-mimetype
meillo@102	2107 script.
meillo@112	2108 .Ci 4b5944268ea0da7bb30598a27857304758ea9b44
meillo@102	2109 Using it is the default choice.
meillo@102	2110 .P
meillo@112	2111 A far better, though less portable, approach is the use of
meillo@102	2112 .Pn file .
meillo@102	2113 This standard tool tries to determine the type of files.
meillo@102	2114 Unfortunately, its capabilities and accuracy varies from system to system.
meillo@102	2115 Additionally, its output was only intended for human beings,
meillo@102	2116 but not to be used by programs.
meillo@102	2117 It varies much.
meillo@102	2118 Nevertheless, modern versions of GNU
meillo@102	2119 .Pn file ,
meillo@102	2120 which is prevalent on the popular GNU/Linux systems,
meillo@102	2121 provides MIME type output in machine-readable form.
meillo@102	2122 Although this solution is highly system-dependent,
meillo@102	2123 it solves the difficult problem well.
meillo@102	2124 On systems where GNU
meillo@102	2125 .Pn file ,
meillo@102	2126 version 5.04 or higher, is available it should be used.
meillo@102	2127 One needs to specify the following profile entry to do so:
meillo@112	2128 .Ci 3baec236a39c5c89a9bda8dbd988d643a21decc6
meillo@102	2129 .VS
meillo@102	2130 Mime-Type-Query: file -b --mime
meillo@102	2131 VE
meillo@102	2132 .LP
meillo@102	2133 Other versions of
meillo@102	2134 .Pn file
meillo@102	2135 might possibly be usable with wrapper scripts to reformat the output.
meillo@102	2136 The diversity among
meillo@102	2137 .Pn file
meillo@102	2138 implementations is great; one needs to check the local variant.
meillo@102	2139 .P
meillo@102	2140 If no MIME type can be determined, text content gets sent as
meillo@102	2141 `text/plain' and anything else under the generic fall-back type
meillo@102	2142 `application/octet-stream'.
meillo@102	2143 It is not possible in mmh to override the automatic MIME type guessing
meillo@102	2144 for a specific file.
meillo@102	2145 To do so, the user would need to know in advance for which file
meillo@102	2146 the automatic guessing does fail, or the system would require interaction.
meillo@102	2147 I consider both cases impractical.
meillo@102	2148 The existing solution should be sufficient.
meillo@102	2149 If not, the user may always fall back to
meillo@102	2150 .Pn mhbuild
meillo@102	2151 composition drafts and ignore the attachment system.
meillo@101	2152
meillo@102	2153
meillo@102	2154 .U3 "Storing Attachments
meillo@102	2155 .P
meillo@108	2156 Extracting MIME parts of a message and storing them to disk is done by
meillo@108	2157 .Pn mhstore .
meillo@108	2158 The program has two operation modes,
meillo@108	2159 .Sw -auto
meillo@108	2160 and
meillo@108	2161 .Sw -noauto .
meillo@108	2162 With the former one, each part is stored under the filename given in the
meillo@108	2163 MIME part's meta information, if available.
meillo@108	2164 This naming information is usually available for modern attachments.
meillo@108	2165 If no filename is available, this MIME part is stored as if
meillo@108	2166 .Sw -noauto
meillo@108	2167 would have been specified.
meillo@108	2168 In the
meillo@108	2169 .Sw -noauto
meillo@108	2170 mode, the parts are processed according to rules, defined by
meillo@108	2171 .Pe mhstore-store-*
meillo@108	2172 profile entries.
meillo@108	2173 These rules define generic filename templates for storing
meillo@108	2174 or commands to post-process the contents in arbitrary ways.
meillo@108	2175 If no matching rule is available the part is stored under a generic
meillo@108	2176 filename, built from message number, MIME part number, and MIME type.
meillo@108	2177 .P
meillo@108	2178 The
meillo@108	2179 .Sw -noauto
meillo@108	2180 mode had been the default in nmh because it was considered safe,
meillo@108	2181 in contrast to the
meillo@108	2182 .Sw -auto
meillo@108	2183 mode.
meillo@108	2184 In mmh,
meillo@108	2185 .Sw -auto
meillo@108	2186 is not dangerous anymore.
meillo@108	2187 Two changes were necessary:
meillo@108	2188 .BU
meillo@108	2189 Any directory path is removed from the proposed filename.
meillo@108	2190 Thus, the files are always stored in the expected directory.
meillo@108	2191 .Ci 41b6eadbcecf63c9a66aa5e582011987494abefb
meillo@108	2192 .BU
meillo@108	2193 Tar files are not extracted automatically any more.
meillo@108	2194 Thus, the rest of the file system will not be touched.
meillo@108	2195 .Ci 94c80042eae3383c812d9552089953f9846b1bb6
meillo@108	2196 .LP
meillo@108	2197 Now, the outcome of mmh's
meillo@108	2198 .Cl "mhstore -auto
meillo@110	2199 can be foreseen from the output of
meillo@108	2200 .Cl "mhlist -verbose" .
meillo@108	2201 .P
meillo@108	2202 The
meillo@108	2203 .Sw -noauto
meillo@108	2204 mode is seen to be more powerful but less convenient.
meillo@108	2205 On the other hand,
meillo@108	2206 .Sw -auto
meillo@108	2207 is safe now and
meillo@108	2208 storing attachments under their original name is intuitive.
meillo@108	2209 Hence,
meillo@108	2210 .Sw -auto
meillo@108	2211 serves better as the default option.
meillo@108	2212 .Ci 3410b680416c49a7617491af38bc1929855a331d
meillo@108	2213 .P
meillo@108	2214 Files are stored into the directory given by the
meillo@108	2215 .Pe Nmh-Storage
meillo@108	2216 profile entry, if set, or
meillo@108	2217 into the current working directory, otherwise.
meillo@108	2218 Storing to different directories is only possible with
meillo@108	2219 .Pe mhstore-store-*
meillo@108	2220 profile entries.
meillo@108	2221 .P
meillo@108	2222 Still, in both modes, existing files get overwritten silently.
meillo@108	2223 This can be considered a bug.
meillo@108	2224 Yet, each other behavior has its draw-backs, too.
meillo@108	2225 Refusing to replace files requires adding a
meillo@108	2226 .Sw -force
meillo@108	2227 option.
meillo@108	2228 Users will likely need to invoke
meillo@108	2229 .Pn mhstore
meillo@108	2230 a second time with
meillo@108	2231 .Sw -force
meillo@108	2232 then.
meillo@108	2233 Eventually, only the user can decide in the concrete case.
meillo@108	2234 This requires interaction, which I like to avoid if possible.
meillo@108	2235 Appending a unique suffix to the filename is another bad option.
meillo@108	2236 For now, the behavior remains as it is.
meillo@108	2237 .P
meillo@108	2238 In mmh, only MIME parts of type message are special in
meillo@108	2239 .Pn mhstore 's
meillo@108	2240 .Sw -auto
meillo@108	2241 mode.
meillo@108	2242 Instead of storing message/rfc822 parts as files to disk,
meillo@108	2243 they are stored as messages into the current mail folder.
meillo@108	2244 The same applies to message/partial, only, the parts are reassembled
meillo@108	2245 automatically before.
meillo@108	2246 Parts of type message/external-body are not automatically retrieved
meillo@108	2247 anymore. Instead, Information on how to retrieve them is output.
meillo@108	2248 Not supporting this rare case saved nearly one thousand lines of code.
meillo@108	2249 .Ci 55e1d8c654ee0f7c45b9361ce34617983b454c32
meillo@108	2250 .\" XXX mention somewhere else too: (The profile entry `nmh-access-ftp'
meillo@108	2251 .\" and sbr/ruserpass.c for reading ~/.netrc are gone now.)
meillo@108	2252 Not special anymore is `application/octet-stream; type=tar'.
meillo@108	2253 Automatically extracting such MIME parts had been the dangerous part
meillo@108	2254 of the
meillo@108	2255 .Sw -auto
meillo@108	2256 mode.
meillo@108	2257 .Ci 94c80042eae3383c812d9552089953f9846b1bb6
meillo@108	2258
meillo@102	2259
meillo@102	2260
meillo@102	2261 .U3 "Showing MIME Messages
meillo@102	2262 .P
meillo@114	2263 The program
meillo@114	2264 .Pn mhshow
meillo@114	2265 had been written to display MIME messages.
meillo@114	2266 It implemented the conceptional view of the MIME RFCs.
meillo@114	2267 Nmh's
meillo@114	2268 .Pn mhshow
meillo@114	2269 handled each MIME part independently, presenting them separately
meillo@114	2270 to the user.
meillo@114	2271 This does not match today's understanding of email attachments,
meillo@114	2272 where displaying a message is seen to be a single, integrated operation.
meillo@114	2273 Today, email messages are expected to consist of a main text part
meillo@114	2274 plus possibly attachments.
meillo@114	2275 They are not any more seen to be arbitrary MIME hierarchies with
meillo@114	2276 information on how to display the individual parts.
meillo@114	2277 I adjusted
meillo@114	2278 .Pn mhshow 's
meillo@114	2279 behavior to the modern view on the topic.
meillo@114	2280 .P
meillo@114	2281 Note that this section completely ignores the original
meillo@114	2282 .Pn show
meillo@114	2283 program, because it was not capable to display MIME messages
meillo@114	2284 and is no longer part of mmh.
meillo@114	2285 Although
meillo@114	2286 .Pn mhshow
meillo@114	2287 was renamed to
meillo@114	2288 .Pn show
meillo@114	2289 in mmh, this section uses the name
meillo@114	2290 .Pn mhshow ,
meillo@114	2291 in order to avoid confusion.
meillo@114	2292 .P
meillo@114	2293 In mmh, the basic idea is that
meillo@114	2294 .Pn mhshow
meillo@114	2295 should display a message in one single pager session.
meillo@114	2296 Therefore,
meillo@114	2297 .Pn mhshow
meillo@114	2298 invokes a pager session for all its output,
meillo@114	2299 whenever it prints to a terminal.
meillo@114	2300 .Ci a4197ea6ffc5c1550e8b52d5a654bcaaaee04a4e
meillo@114	2301 In consequence,
meillo@114	2302 .Pn mhl
meillo@114	2303 does no more invoke a pager.
meillo@114	2304 .Ci 0e46503be3c855bddaeae3843e1b659279c35d70
meillo@114	2305 With
meillo@114	2306 .Pn mhshow
meillo@114	2307 replacing the original
meillo@114	2308 .Pn show ,
meillo@114	2309 output from
meillo@114	2310 .Pn mhl
meillo@114	2311 does not go to the terminal directly, but through
meillo@114	2312 .Pn mhshow .
meillo@114	2313 Hence,
meillo@114	2314 .Pn mhl
meillo@114	2315 does not need to invoke a pager.
meillo@114	2316 The one and only job of
meillo@114	2317 .Pn mhl
meillo@114	2318 is to format messages or parts of them.
meillo@114	2319 The only place in mmh, where a pager is invoked is
meillo@114	2320 .Pn mhshow .
meillo@114	2321 .P
meillo@114	2322 .Pe mhshow-show-*
meillo@114	2323 profile entries can be used to display MIME parts in a specific way.
meillo@114	2324 For instance, PDF and Postscript files could be converted to plain text
meillo@114	2325 to display them in the terminal.
meillo@114	2326 In mmh, the displaying of MIME parts will always be done serially.
meillo@114	2327 The request to display the MIME type `multipart/parallel' in parallel
meillo@114	2328 is ignored.
meillo@114	2329 It is simply treated as `multipart/mixed'.
meillo@114	2330 .Ci d0581ba306a7299113a346f9b4c46ce97bc4cef6
meillo@114	2331 This could already be requested with the, now removed,
meillo@114	2332 .Sw -serialonly
meillo@114	2333 switch of
meillo@114	2334 .Pn mhshow .
meillo@114	2335 As MIME parts are always processed exclusively , i.e. serially,
meillo@114	2336 the `%e' escape in
meillo@114	2337 .Pe mhshow-show-*
meillo@114	2338 profile entries became useless and was thus removed.
meillo@114	2339 .Ci a20d405db09b7ccca74d3e8c57550883da49e1ae
meillo@114	2340 .P
meillo@114	2341 In the intended setup, only text content would be displayed.
meillo@114	2342 Non-text content would be converted to text by appropriate
meillo@114	2343 .Pe mhshow-show-*
meillo@114	2344 profile entries before, if possible and wanted.
meillo@114	2345 All output would be displayed in a single pager session.
meillo@114	2346 Other kinds of attachments are ignored.
meillo@114	2347 With
meillo@114	2348 .Pe mhshow-show-*
meillo@114	2349 profile entries for them, they can be displayed serially along
meillo@114	2350 the message.
meillo@114	2351 For parallel display, the attachments need to be stored to disk first.
meillo@114	2352 .P
meillo@114	2353 To display text content in foreign charsets, they need to be converted
meillo@114	2354 to the native charset.
meillo@114	2355 Therefore,
meillo@114	2356 .Pe mhshow-charset-*
meillo@114	2357 profile entries used to be needed.
meillo@121	2358 In mmh, the conversion is done automatically by piping the text through
meillo@114	2359 the
meillo@114	2360 .Pn iconv
meillo@114	2361 command, if necessary.
meillo@114	2362 .Ci 2433122c20baccb10b70b49c04c6b0497b5b3b60
meillo@114	2363 Custom
meillo@114	2364 .Pe mhshow-show-*
meillo@114	2365 rules for textual content might need a
meillo@114	2366 .Cl "iconv -f %c %f \|
meillo@114	2367 prefix to have the text converted to the native charset.
meillo@114	2368 .P
meillo@121	2369 Although the conversion of foreign charsets to the native one
meillo@114	2370 has improved, it is not consistent enough.
meillo@114	2371 Further work needs to be done and
meillo@114	2372 the basic concepts in this field need to be re-thought.
meillo@114	2373 Though, the default setup of mmh displays message in foreign charsets
meillo@114	2374 correctly without the need to configure anything.
meillo@114	2375
meillo@114	2376
meillo@114	2377 .ig
meillo@114	2378
meillo@114	2379 .P
meillo@114	2380 mhshow/mhstore: Removed support for retrieving message/external-body parts.
meillo@114	2381 These tools won't download the contents automatically anymore. Instead,
meillo@114	2382 they print the information needed to get the contents. If someone should
meillo@114	2383 really receive one of those rare message/external-body messages, he can
meillo@114	2384 do the job manually. We save nearly a thousand lines of code. That's worth
meillo@114	2385 it!
meillo@114	2386 (The profile entry `nmh-access-ftp' and sbr/ruserpass.c for reading
meillo@114	2387 ~/.netrc are gone now.)
meillo@114	2388 .Ci 55e1d8c654ee0f7c45b9361ce34617983b454c32
meillo@114	2389
meillo@114	2390 ..
meillo@102	2391
meillo@58	2392
meillo@58	2393
meillo@58	2394 .H2 "Digital Cryptography
meillo@22	2395 .P
meillo@58	2396 Signing and encryption.
meillo@112	2397 .P
meillo@112	2398 FIXME
meillo@58	2399
meillo@58	2400
meillo@102	2401
meillo@133	2402 .H2 "Draft and Trash Folder
meillo@131	2403 .P
meillo@58	2404
meillo@131	2405 .U3 "Draft Folder
meillo@131	2406 .P
meillo@131	2407 In the beginning, MH had the concept of a draft message.
meillo@131	2408 This is the file
meillo@131	2409 .Fn draft
meillo@131	2410 in the MH directory, which is treated special.
meillo@131	2411 On composing a message, this draft file was used.
meillo@131	2412 As the draft file was one particular file, only one draft could be
meillo@131	2413 managed at any time.
meillo@131	2414 When starting to compose another message before the former one was sent,
meillo@131	2415 the user had to decide among:
meillo@131	2416 .BU
meillo@131	2417 Use the old draft to finish and send it before starting with a new one.
meillo@131	2418 .BU
meillo@131	2419 Discard the old draft, replacing it with the new one.
meillo@131	2420 .BU
meillo@131	2421 Preserve the old draft by refiling it to a folder.
meillo@131	2422 .P
meillo@131	2423 This was, it was only possible to work in alternation on multiple drafts.
meillo@131	2424 Therefore, the current draft needed to be refiled to a folder and
meillo@131	2425 another one re-using for editing.
meillo@131	2426 Working on multiple drafts at the same time was impossible.
meillo@131	2427 The usual approach of switching to a different MH context did not
meillo@131	2428 change anything.
meillo@131	2429 .P
meillo@131	2430 The draft folder facility exists to
meillo@131	2431 allow true parallel editing of drafts, in a straight forward way.
meillo@131	2432 It was introduced by Marshall T. Rose, already in 1984.
meillo@131	2433 Similar to other new features, the draft folder was inactive by default.
meillo@131	2434 Even in nmh, the highly useful draft folder was not available
meillo@131	2435 out-of-the-box.
meillo@131	2436 At least, Richard Coleman added the man page
meillo@131	2437 .Mp mh-draft (5)
meillo@131	2438 to better document the feature.
meillo@131	2439 .P
meillo@131	2440 Not using the draft folder facility has the single advantage of having
meillo@131	2441 the draft file at a static location.
meillo@131	2442 This is simple in simple cases but the concept does not scale for more
meillo@131	2443 complex cases.
meillo@131	2444 The concept of the draft message is too limited for the problem.
meillo@131	2445 Therefore the draft folder was introduced.
meillo@131	2446 It is the more powerful and more natural concept.
meillo@131	2447 The draft folder is a folder like any other folder in MH.
meillo@131	2448 Its messages can be listed like any other messages.
meillo@131	2449 A draft message is no longer a special case.
meillo@131	2450 Tools do not need special switches to work on the draft message.
meillo@131	2451 Hence corner-cases were removed.
meillo@131	2452 .P
meillo@131	2453 The trivial part of the work was activating the draft folder with a
meillo@131	2454 default name.
meillo@131	2455 I chose the name
meillo@131	2456 .Fn +drafts
meillo@131	2457 for obvious reasons.
meillo@131	2458 In consequence, the command line switches
meillo@131	2459 .Sw -draftfolder
meillo@131	2460 and
meillo@131	2461 .Sw -draftmessage
meillo@131	2462 could be removed.
meillo@131	2463 More difficult but also more improving was updating the tools to the
meillo@131	2464 new concept.
meillo@131	2465 For nearly three decades, the tools needed to support two draft handling
meillo@131	2466 approaches.
meillo@131	2467 By fully switching to the draft folder, the tools could be simplified
meillo@131	2468 by dropping the awkward draft message handling code.
meillo@131	2469 .Sw -draft
meillo@131	2470 switches were removed because operating on a draft message is no longer
meillo@131	2471 special.
meillo@131	2472 It became indistinguishable to operating on any other message.
meillo@131	2473 There is no more need to query the user for draft handling.
meillo@131	2474 It is always possible to add another new draft.
meillo@131	2475 Refiling drafts is without difference to refiling other messages.
meillo@131	2476 All these special cases are gone.
meillo@131	2477 Yet, one draft-related switch remained.
meillo@131	2478 .Pn comp
meillo@131	2479 still has
meillo@131	2480 .Sw -[no]use
meillo@131	2481 for switching between two modes:
meillo@131	2482 .BU
meillo@131	2483 .Sw -use :
meillo@131	2484 Modify an existing draft.
meillo@131	2485 .BU
meillo@131	2486 .Sw -nouse :
meillo@131	2487 Compose a new draft, possibly taking some existing message as a form.
meillo@131	2488 .P
meillo@131	2489 In either case, the behavior of
meillo@131	2490 .Pn comp
meillo@131	2491 is deterministic.
meillo@131	2492 .P
meillo@131	2493 .Pn send
meillo@131	2494 now operates on the current message in the draft folder by default.
meillo@131	2495 As message and folder can both be overridden by specifying them on
meillo@131	2496 the command line, it is possible to send any message in the mail storage
meillo@131	2497 by simply specifying its number and folder.
meillo@131	2498 In contrast to the other tools,
meillo@131	2499 .Pn send
meillo@131	2500 takes the draft folder as its default folder.
meillo@131	2501 .P
meillo@131	2502 Dropping the draft message concept in favor for the draft folder concept,
meillo@131	2503 removed special cases with regular cases.
meillo@131	2504 This simplified the source code of the tools, as well as the concepts.
meillo@131	2505 In mmh, draft management does not break with the MH concepts
meillo@131	2506 but applies them.
meillo@133	2507 .Cl "scan +drafts" ,
meillo@133	2508 for instance, is a truly natural request.
meillo@131	2509 Most of the work was already done by Rose in the eighties.
meillo@133	2510 The original improvement of mmh is dropping the old draft message approach
meillo@133	2511 and thus simplifying the tools, the documentation and the system as a whole.
meillo@131	2512 Although my part in the draft handling improvement was small,
meillo@133	2513 it was an important one.
meillo@131	2514
meillo@131	2515
meillo@131	2516 .U3 "Trash Folder
meillo@131	2517 .P
meillo@131	2518 Similar to the situation for drafts is the situation for removed messages.
meillo@131	2519 Historically, a message was ``deleted'' by prepending a specific
meillo@131	2520 \fIbackup prefix\fP, usually the comma character,
meillo@131	2521 to the file name.
meillo@131	2522 The specific message would vanish from MH because only files with
meillo@131	2523 non-digit characters in their name are not treated as messages.
meillo@131	2524 Although files remained in the file system,
meillo@131	2525 the messages were no more visible in MH.
meillo@131	2526 To truly delete them, a maintenance job is needed.
meillo@131	2527 Usually a cron job is installed to delete them after a grace time.
meillo@131	2528 For instance:
meillo@131	2529 .VS
meillo@131	2530 find $HOME/Mail -type f -name ',*' -ctime +7 -delete
meillo@131	2531 VE
meillo@131	2532 In such a setup, the original message can be restored
meillo@131	2533 within the grace time interval by stripping the
meillo@131	2534 the backup prefix from the file name.
meillo@131	2535 But one can not rely on this statement.
meillo@131	2536 If the last message of a folder with six messages (1-6) is removed,
meillo@131	2537 message
meillo@131	2538 .Fn 6 ,
meillo@131	2539 becomes file
meillo@131	2540 .Fn ,6 .
meillo@131	2541 If then a new message enters the same folder, it will be given
meillo@131	2542 the number one higher than the highest existing message.
meillo@131	2543 In this case the message is named
meillo@131	2544 .Fn 6
meillo@131	2545 then.
meillo@131	2546 If this message is removed as well,
meillo@131	2547 then the backup of the former message gets overwritten.
meillo@131	2548 Hence, the ability to restore removed messages does not only depend on
meillo@131	2549 the ``sweeping cron job'' but also on the removing of further messages.
meillo@131	2550 It is undesirable to have such obscure and complex mechanisms.
meillo@131	2551 The user should be given a small set of clear assertions.
meillo@131	2552 ``Removed files are restorable within a seven-day grace time.''
meillo@131	2553 is such a clear assertion.
meillo@131	2554 With the addition ``... unless a message with the same name in the
meillo@131	2555 same folder is removed before.'' the statement becomes complex.
meillo@131	2556 A user will hardly be able to keep track of any removal to know
meillo@131	2557 if the assertion still holds true for a specific file.
meillo@131	2558 The the real mechanism is practically obscure to the user.
meillo@131	2559 The consequences of further removals are not obvious.
meillo@131	2560 .P
meillo@131	2561 Further more, the backup files are scattered within the whole mail storage.
meillo@131	2562 This complicates managing them.
meillo@131	2563 It is possible, with help of
meillo@131	2564 .Pn find ,
meillo@131	2565 but everything would be more convenient
meillo@131	2566 if the deleted messages would be collected in one place.
meillo@131	2567 .P
meillo@131	2568 The profile entry
meillo@131	2569 .Pe rmmproc
meillo@131	2570 (previously named
meillo@131	2571 .Pe Delete-Prog )
meillo@131	2572 was introduced very early to improve the situation.
meillo@131	2573 It could be set to any command, which would be executed to removed
meillo@131	2574 the specified messages.
meillo@131	2575 This would override the default action, described above.
meillo@131	2576 Refiling the to-be-removed files to a garbage folder is the usual example.
meillo@131	2577 Nmh's man page
meillo@131	2578 .Mp rmm (1)
meillo@131	2579 proposes to set the
meillo@131	2580 .Pe rmmproc
meillo@131	2581 to
meillo@131	2582 .Cl "refile +d
meillo@131	2583 to move messages to the garbage folder,
meillo@131	2584 .Fn +d ,
meillo@131	2585 instead of renaming them with the backup prefix.
meillo@131	2586 The man page proposes additionally the expunge command
meillo@131	2587 .Cl "rm `mhpath +d all`
meillo@131	2588 to empty the garbage folder.
meillo@131	2589 .P
meillo@131	2590 Removing messages in such a way has advantages.
meillo@131	2591 The mail storage is prevented from being cluttered with removed messages
meillo@131	2592 because they are all collected in one place.
meillo@131	2593 Existing and removed messages are thus separated more strictly.
meillo@131	2594 No backup files are silently overwritten.
meillo@131	2595 Most important is the ability to keep removed messages in the MH domain.
meillo@131	2596 Messages in the trash folder can be listed like those in any other folder.
meillo@131	2597 Deleted messages can be displayed like any other messages.
meillo@131	2598 Restoring a deleted messages can be done with
meillo@131	2599 .Pn refile .
meillo@131	2600 All operations on deleted files are still covered by the MH tools.
meillo@131	2601 The trash folder is just like any other folder in the mail storage.
meillo@131	2602 .P
meillo@131	2603 Similar to the draft folder case, I dropped the old backup prefix approach
meillo@131	2604 in favor for replacing it by the better suiting trash folder system.
meillo@131	2605 Hence,
meillo@131	2606 .Pn rmm
meillo@131	2607 calls
meillo@131	2608 .Pn refile
meillo@131	2609 to move the to-be-removed message to the trash folder,
meillo@131	2610 .Fn +trash
meillo@131	2611 by default.
meillo@131	2612 To sweep it clean, one can use
meillo@131	2613 .Cl "rmm -unlink +trash a" ,
meillo@131	2614 where the
meillo@131	2615 .Sw -unlink
meillo@131	2616 switch causes the files to be unlinked.
meillo@131	2617 .P
meillo@131	2618 Dropping the legacy approach and completely converting to the new approach
meillo@131	2619 simplified the code base.
meillo@131	2620 The relationship between
meillo@131	2621 .Pn rmm
meillo@131	2622 and
meillo@131	2623 .Pn refile
meillo@131	2624 was inverted.
meillo@131	2625 In mmh,
meillo@131	2626 .Pn rmm
meillo@131	2627 invokes
meillo@131	2628 .Pn refile ,
meillo@131	2629 which used to be the other way round.
meillo@131	2630 Yet, the relationship is simpler now.
meillo@131	2631 No more can loops, like described in nmh's man page for
meillo@131	2632 .Mp refile (1),
meillo@131	2633 occur:
meillo@131	2634 .QS
meillo@131	2635 Since
meillo@131	2636 .Pn refile
meillo@131	2637 uses your
meillo@131	2638 .Pe rmmproc
meillo@131	2639 to delete the message, the
meillo@131	2640 .Pe rmmproc
meillo@131	2641 must NOT call
meillo@131	2642 .Pn refile
meillo@131	2643 without specifying
meillo@131	2644 .Sw -normmproc
meillo@131	2645 or you will create an infinite loop.
meillo@131	2646 .QE
meillo@131	2647 .LP
meillo@131	2648 .Pn rmm
meillo@131	2649 either unlinks a message with
meillo@131	2650 .Fu unlink()
meillo@131	2651 or invokes
meillo@131	2652 .Pn refile
meillo@131	2653 to move it to the trash folder.
meillo@131	2654 .Pn refile
meillo@131	2655 does not invoke any tools.
meillo@131	2656 .P
meillo@131	2657
meillo@131	2658
meillo@131	2659
meillo@131	2660 Keeping unused alternative in the code is a bad choice as they likely
meillo@131	2661 gather bugs, by not being constantly tested.
meillo@131	2662 Also, the increased code
meillo@131	2663 size and more conditions crease the maintenance costs.
meillo@131	2664
meillo@131	2665 By generalizing the message removal in a way that it becomes covered
meillo@131	2666 by the MH concepts makes the whole system more powerful.
meillo@131	2667
meillo@131	2668
meillo@131	2669
meillo@131	2670
meillo@133	2671 .H2 "Modern Defaults
meillo@133	2672 .P
meillo@133	2673 Nmh has a bunch of convenience-improving features inactive by default,
meillo@133	2674 although one can expect every new user wanting to have them active.
meillo@133	2675 The reason they are inactive by default is the wish to stay compatible
meillo@133	2676 with old versions.
meillo@133	2677 But what is the definition for old versions.
meillo@133	2678 Still, the highly useful draft folder facility is not active by default
meillo@133	2679 although it had been introduced over twenty-five years ago
meillo@133	2680 .[
meillo@133	2681 rose romine real work
meillo@133	2682 .]
meillo@133	2683 \(en the community seems not to care.
meillo@133	2684 This is one of several examples that require new users to build up
meillo@133	2685 their profile before they can access the modern features of nmh.
meillo@133	2686 Without an extensively built-up profile, the setup is hardly usable
meillo@133	2687 for modern emailing.
meillo@133	2688 The point is not the customization of the setup,
meillo@133	2689 but the activating of generally useful facilities.
meillo@133	2690 .P
meillo@133	2691 Yet, the real problem lies less in enabling the features, as this is
meillo@133	2692 straight forward as soon as one knows what he wants.
meillo@133	2693 The real problem is that new users need deep insights into the project
meillo@133	2694 before they find out what they are missing and that nmh actually
meillo@133	2695 provides it already, it just was not activated.
meillo@133	2696 To give an example, I needed one year of using nmh
meillo@133	2697 before I became aware of the existence of the attachment system.
meillo@133	2698 One could argue that this fact disqualifies my reading of the
meillo@133	2699 documentation.
meillo@133	2700 If I would have installed nmh from source back then, I could agree.
meillo@133	2701 Yet, I had used a prepackaged version and had expected that it would
meillo@133	2702 just work.
meillo@133	2703 Nevertheless, I had been convinced by the concepts of MH already
meillo@133	2704 and I am a software developer,
meillo@133	2705 still I required a lot of time to discover the cool features.
meillo@133	2706 How can we expect users to be even more advanced than me,
meillo@133	2707 just to allow them use MH in a convenient and modern way?
meillo@133	2708 Unless they are strongly convinced of the concepts, they will fail.
meillo@133	2709 I have seen friends of me giving up disappointed
meillo@133	2710 before they truly used the system,
meillo@133	2711 although they had been motivated in the beginning.
meillo@133	2712 They suffer hard enough to get used to the toolchest approach,
meillo@133	2713 we should spare them further inconveniences.
meillo@133	2714 .P
meillo@133	2715 Maintaining compatibility for its own sake is for no good.
meillo@133	2716 If any MH implementation would be the back-end of widespread
meillo@133	2717 email clients with large user bases, compatibility would be more
meillo@133	2718 important.
meillo@133	2719 Yet, it appears as if this is not the case.
meillo@133	2720 Hence, compatibility is hardly important for technical reasons.
meillo@133	2721 Its importance originates rather from personal reasons.
meillo@133	2722 Nmh's user base is small and old.
meillo@133	2723 Changing the interfaces would cause inconvenience to long-term users of MH.
meillo@133	2724 It would force them to change their many years old MH configurations.
meillo@133	2725 I do understand this aspect, but it keeps new users from using MH.
meillo@133	2726 By sticking to the old users, new users are kept away.
meillo@133	2727 Yet, the future lies in new users.
meillo@133	2728 Hence, mmh invites new users by providing a convenient and modern setup,
meillo@133	2729 readily usable out-of-the-box.
meillo@133	2730 .P
meillo@133	2731 In mmh, all modern features are active by default.
meillo@133	2732 In consequence, a setup with a profile that defines only the path to the
meillo@133	2733 mail storage, is already convenient to use.
meillo@133	2734 Again, Paul Vixie's ``edginess'' appeal supports the direction I took:
meillo@133	2735 ``the `main branch' should just be modern''.
meillo@133	2736 .[
meillo@133	2737 paul vixie edginess nmh-workers
meillo@133	2738 .]
meillo@133	2739 .P
meillo@133	2740 Modern features that are active in mmh by default include:
meillo@133	2741 .BU
meillo@133	2742 The attachment system (\c
meillo@133	2743 .Hd Attach ).
meillo@133	2744 .Ci 8ff284ff9167eff8f5349481529332d59ed913b1
meillo@133	2745 .BU
meillo@133	2746 The draft folder facility (\c
meillo@133	2747 .Fn +drafts ).
meillo@133	2748 .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@133	2749 .BU
meillo@133	2750 The unseen sequence (`u')
meillo@133	2751 .Ci c2360569e1d8d3678e294eb7c1354cb8bf7501c1
meillo@133	2752 and the sequence negation prefix (`!').
meillo@133	2753 .Ci db74c2bd004b2dc9bf8086a6d8bf773ac051f3cc
meillo@133	2754 .BU
meillo@133	2755 Quoting the original message in the reply.
meillo@133	2756 .Ci 67411b1f95d6ec987b4c732459e1ba8a8ac192c6
meillo@133	2757 .BU
meillo@133	2758 Forwarding messages using MIME.
meillo@133	2759 .Ci 6e271608b7b9c23771523f88d23a4d3593010cf1
meillo@131	2760
meillo@133	2761
meillo@133	2762
meillo@133	2763
meillo@133	2764
meillo@133	2765 .\" --------------------------------------------------------------
meillo@131	2766 .H1 "Styling
meillo@22	2767 .P
meillo@118	2768 Kernighan and Pike have emphasized the importance of style in the
meillo@118	2769 preface of their book:
meillo@118	2770 .[ [
meillo@118	2771 kernighan pike practice of programming
meillo@118	2772 .], p. x]
meillo@118	2773 .QS
meillo@118	2774 Chapter 1 discusses programming style.
meillo@118	2775 Good style is so important to good programming that we have chose
meillo@118	2776 to cover it first.
meillo@118	2777 .QE
meillo@118	2778 This section covers changes in mmh that were motivated by the desire
meillo@118	2779 to improve on style.
meillo@118	2780 Many of them follow the rules given in the quoted book.
meillo@118	2781 .[
meillo@118	2782 kernighan pike practice of programming
meillo@118	2783 .]
meillo@118	2784
meillo@118	2785
meillo@127	2786
meillo@127	2787
meillo@127	2788 .H2 "Code Style
meillo@118	2789 .P
meillo@118	2790 .U3 "Indentation Style
meillo@118	2791 .P
meillo@118	2792 Indentation styles are the holy cow of programmers.
meillo@118	2793 Again Kernighan and Pike:
meillo@118	2794 .[ [
meillo@118	2795 kernighan pike practice of programming
meillo@118	2796 .], p. 10]
meillo@118	2797 .QS
meillo@118	2798 Programmers have always argued about the layout of programs,
meillo@118	2799 but the specific style is much less important than its consistent
meillo@118	2800 application.
meillo@121	2801 Pick one style, preferably ours, use it consistently, and don't waste
meillo@118	2802 time arguing.
meillo@118	2803 .QE
meillo@118	2804 .P
meillo@118	2805 I agree that the constant application is most important,
meillo@118	2806 but I believe that some styles have advantages over others.
meillo@118	2807 For instance the indentation with tab characters only.
meillo@118	2808 Tab characters directly map to the nesting level \(en
meillo@118	2809 one tab, one level.
meillo@118	2810 Tab characters are flexible because developers can adjust them to
meillo@118	2811 whatever width they like to have.
meillo@118	2812 There is no more need to run
meillo@118	2813 .Pn unexpand
meillo@118	2814 or
meillo@118	2815 .Pn entab
meillo@118	2816 programs to ensure the correct mixture of leading tabs and spaces.
meillo@118	2817 The simple rules are: (1) Leading whitespace must consist of tabs only.
meillo@118	2818 (2) Any other whitespace should consist of spaces.
meillo@121	2819 These two rules ensure the integrity of the visual appearance.
meillo@121	2820 Although reformatting existing code should be avoided, I did it.
meillo@118	2821 I did not waste time arguing; I just did it.
meillo@118	2822 .Ci a485ed478abbd599d8c9aab48934e7a26733ecb1
meillo@118	2823
meillo@118	2824 .U3 "Comments
meillo@118	2825 .P
meillo@118	2826 Section 1.6 of
meillo@118	2827 .[ [
meillo@118	2828 kernighan pike practice of programming
meillo@118	2829 .], p. 23]
meillo@118	2830 demands: ``Don't belabor the obvious.''
meillo@122	2831 Hence, I simply removed all the comments in the following code excerpt:
meillo@118	2832 .VS
meillo@120	2833 context_replace(curfolder, folder); /* update current folder */
meillo@120	2834 seq_setcur(mp, mp->lowsel); /* update current message */
meillo@120	2835 seq_save(mp); /* synchronize message sequences */
meillo@120	2836 folder_free(mp); /* free folder/message structure */
meillo@120	2837 context_save(); /* save the context file */
meillo@120	2838
meillo@120	2839 [...]
meillo@120	2840
meillo@120	2841 int c; /* current character */
meillo@120	2842 char cp; / miscellaneous character pointer */
meillo@120	2843
meillo@120	2844 [...]
meillo@120	2845
meillo@120	2846 /* NUL-terminate the field */
meillo@120	2847 *cp = '\0';
meillo@118	2848 VE
meillo@120	2849 .Ci 426543622b377fc5d091455cba685e114b6df674
meillo@118	2850 .P
meillo@118	2851 The names of the functions explain enough already.
meillo@118	2852
meillo@118	2853 .U3 "Names
meillo@118	2854 .P
meillo@118	2855 Kernighan and Pike suggest:
meillo@118	2856 ``Use active names for functions''.
meillo@118	2857 .[ [
meillo@118	2858 kernighan pike practice of programming
meillo@118	2859 .], p. 4]
meillo@118	2860 One application of this rule was the rename of
meillo@118	2861 .Fu check_charset()
meillo@118	2862 to
meillo@118	2863 .Fu is_native_charset() .
meillo@118	2864 .Ci 8d77b48284c58c135a6b2787e721597346ab056d
meillo@118	2865 The same change fixed a violation of ``Be accurate'' as well.
meillo@118	2866 The code did not match the expectation the function suggested,
meillo@118	2867 as it, for whatever reason, only compared the first ten characters
meillo@118	2868 of the charset name.
meillo@118	2869 .P
meillo@118	2870 More important than using active names is using descriptive names.
meillo@118	2871 Renaming the obscure function
meillo@118	2872 .Fu m_unknown()
meillo@118	2873 was a delightful event.
meillo@118	2874 .Ci 611d68d19204d7cbf5bd585391249cb5bafca846
meillo@118	2875 .P
meillo@118	2876 Magic numbers are generally considered bad style.
meillo@118	2877 Obviously, Kernighan and Pike agree:
meillo@118	2878 ``Give names to magic numbers''.
meillo@118	2879 .[ [
meillo@118	2880 kernighan pike practice of programming
meillo@118	2881 .], p. 19]
meillo@118	2882 One such change was naming the type of input \(en mbox or mail folder \(en
meillo@118	2883 to be scanned:
meillo@118	2884 .VS
meillo@118	2885 #define SCN_MBOX (-1)
meillo@118	2886 #define SCN_FOLD 0
meillo@118	2887 VE
meillo@118	2888 .Ci 7ffb36d28e517a6f3a10272056fc127592ab1c19
meillo@118	2889 .P
meillo@118	2890 The argument
meillo@118	2891 .Ar outnum
meillo@118	2892 of the function
meillo@118	2893 .Fu scan()
meillo@118	2894 in
meillo@118	2895 .Fn uip/scansbr.c
meillo@118	2896 defines the number of the message to be created.
meillo@118	2897 If no message is to be created, the argument is misused to transport
meillo@118	2898 program logic.
meillo@118	2899 This lead to obscure code.
meillo@118	2900 I improved the clarity of the code by introducing two variables:
meillo@118	2901 .VS
meillo@118	2902 int incing = (outnum > 0);
meillo@118	2903 int ismbox = (outnum != 0);
meillo@118	2904 VE
meillo@118	2905 They cover the magic values and are used for conditions.
meillo@118	2906 The variable
meillo@118	2907 .Ar outnum
meillo@118	2908 is only used when it holds an ordinary message number.
meillo@118	2909 .Ci b8b075c77be7794f3ae9ff0e8cedb12b48fd139f
meillo@118	2910 The clarity improvement of the change showed detours in the program logic
meillo@118	2911 of related code parts.
meillo@118	2912 Having the new variables with descriptive names, a more
meillo@121	2913 straight forward implementation became apparent.
meillo@118	2914 Before the clarification was done,
meillo@118	2915 the possibility to improve had not be seen.
meillo@118	2916 .Ci aa60b0ab5e804f8befa890c0a6df0e3143ce0723
meillo@118	2917
meillo@133	2918
meillo@133	2919
meillo@133	2920 .H2 "Structural Rework
meillo@133	2921 .P
meillo@133	2922
meillo@118	2923 .U3 "Rework of \f(CWanno\fP
meillo@118	2924 .P
meillo@118	2925 At the end of their chapter on style,
meillo@118	2926 Kernighan and Pike ask: ``But why worry about style?''
meillo@121	2927 The following example of my rework of
meillo@118	2928 .Pn anno
meillo@121	2929 provides an answer why style is important in the first place.
meillo@118	2930 .P
meillo@120	2931 Until 2002,
meillo@120	2932 .Pn anno
meillo@120	2933 had six functional command line switches,
meillo@120	2934 .Sw -component
meillo@120	2935 and
meillo@120	2936 .Sw -text ,
meillo@120	2937 which took an argument each,
meillo@120	2938 and the two pairs of flags,
meillo@120	2939 .Sw -[no]date
meillo@120	2940 and
meillo@120	2941 .Sw -[no]inplace.,
meillo@120	2942 .Sw -component
meillo@120	2943 and
meillo@120	2944 .Sw -text ,
meillo@120	2945 which took an argument each,
meillo@120	2946 and the two pairs of flags,
meillo@120	2947 .Sw -[no]date
meillo@120	2948 and
meillo@120	2949 .Sw -[no]inplace .
meillo@120	2950 Then Jon Steinhart introduced his attachment system.
meillo@120	2951 In need for more advanced annotation handling, he extended
meillo@120	2952 .Pn anno .
meillo@120	2953 He added five more switches:
meillo@120	2954 .Sw -draft ,
meillo@120	2955 .Sw -list ,
meillo@120	2956 .Sw -delete ,
meillo@120	2957 .Sw -append ,
meillo@120	2958 and
meillo@120	2959 .Sw -number ,
meillo@120	2960 the last one taking an argument.
meillo@121	2961 .Ci 7480dbc14bc90f2d872d434205c0784704213252
meillo@120	2962 Later,
meillo@120	2963 .Sw -[no]preserve
meillo@120	2964 was added.
meillo@121	2965 .Ci d9b1d57351d104d7ec1a5621f090657dcce8cb7f
meillo@120	2966 Then, the Synopsis section of the man page
meillo@120	2967 .Mp anno (1)
meillo@120	2968 read:
meillo@120	2969 .VS
meillo@120	2970 anno [+folder] [msgs] [-component field] [-inplace \| -noinplace]
meillo@120	2971 [-date \| -nodate] [-draft] [-append] [-list] [-delete]
meillo@120	2972 [-number [num\|all]] [-preserve \| -nopreserve] [-version]
meillo@120	2973 [-help] [-text body]
meillo@120	2974 VE
meillo@120	2975 .LP
meillo@120	2976 The implementation followed the same structure.
meillo@120	2977 Problems became visible when
meillo@120	2978 .Cl "anno -list -number 42
meillo@120	2979 worked on the current message instead on message number 42,
meillo@120	2980 and
meillo@120	2981 .Cl "anno -list -number l:5
meillo@124	2982 did not work on the last five messages but failed with the mysterious
meillo@120	2983 error message: ``anno: missing argument to -list''.
meillo@121	2984 Yet, the invocation matched the specification in the man page.
meillo@120	2985 There, the correct use of
meillo@120	2986 .Sw -number
meillo@120	2987 was defined as being
meillo@120	2988 .Cl "[-number [num\|all]]
meillo@120	2989 and the textual description for the combination with
meillo@120	2990 .Sw -list
meillo@120	2991 read:
meillo@120	2992 .QS
meillo@120	2993 The -list option produces a listing of the field bodies for
meillo@120	2994 header fields with names matching the specified component,
meillo@120	2995 one per line. The listing is numbered, starting at 1, if
meillo@120	2996 the -number option is also used.
meillo@120	2997 .QE
meillo@120	2998 .LP
meillo@120	2999 The problem was manifold.
meillo@120	3000 The code required a numeric argument to the
meillo@120	3001 .Sw -number
meillo@120	3002 switch.
meillo@120	3003 If it was missing or non-numeric,
meillo@120	3004 .Pn anno
meillo@120	3005 aborted with an error message that had an off-by-one error,
meillo@120	3006 printing the switch one before the failing one.
meillo@120	3007 Semantically, the argument to the
meillo@120	3008 .Sw -number
meillo@120	3009 switch is only necessary in combination with
meillo@120	3010 .Sw -delete ,
meillo@120	3011 but not with
meillo@120	3012 .Sw -list .
meillo@120	3013 In the former case it is even necessary.
meillo@120	3014 .P
meillo@120	3015 Trying to fix these problems on the surface would not have solved it truly.
meillo@120	3016 The problems discovered originate from a discrepance between the semantic
meillo@120	3017 structure of the problem and the structure implemented in the program.
meillo@120	3018 Such structural differences can not be cured on the surface.
meillo@120	3019 They need to be solved by adjusting the structure of the implementation
meillo@120	3020 to the structure of the problem.
meillo@120	3021 .P
meillo@120	3022 In 2002, the new switches
meillo@120	3023 .Sw -list
meillo@120	3024 and
meillo@120	3025 .Sw -delete
meillo@120	3026 were added in the same way, the
meillo@120	3027 .Sw -number
meillo@120	3028 switch for instance had been added.
meillo@120	3029 Yet, they are of structural different type.
meillo@120	3030 Semantically,
meillo@120	3031 .Sw -list
meillo@120	3032 and
meillo@120	3033 .Sw -delete
meillo@120	3034 introduce modes of operation.
meillo@120	3035 Historically,
meillo@120	3036 .Pn anno
meillo@120	3037 had only one operation mode: adding header fields.
meillo@120	3038 With the extension, it got two moder modes:
meillo@120	3039 listing and deleting header fields.
meillo@120	3040 The structure of the code changes did not pay respect to this
meillo@120	3041 fundamental change to
meillo@120	3042 .Pn anno 's
meillo@120	3043 behavior.
meillo@120	3044 Neither the implementation nor the documentation did clearly
meillo@120	3045 define them as being exclusive modes of operation.
meillo@120	3046 Having identified the problem, I solved it by putting structure into
meillo@120	3047 .Pn anno
meillo@120	3048 and its documentation.
meillo@120	3049 .Ci d54c8db8bdf01e8381890f7729bc0ef4a055ea11
meillo@120	3050 .P
meillo@120	3051 The difference is visible in both, the code and the documentation.
meillo@121	3052 The following code excerpt:
meillo@120	3053 .VS
meillo@120	3054 int delete = -2; /* delete header element if set */
meillo@120	3055 int list = 0; /* list header elements if set */
meillo@120	3056 [...]
meillo@121	3057 case DELETESW: /* delete annotations */
meillo@121	3058 delete = 0;
meillo@121	3059 continue;
meillo@121	3060 case LISTSW: /* produce a listing */
meillo@121	3061 list = 1;
meillo@121	3062 continue;
meillo@120	3063 VE
meillo@121	3064 .LP
meillo@121	3065 was replaced by:
meillo@120	3066 .VS
meillo@120	3067 static enum { MODE_ADD, MODE_DEL, MODE_LIST } mode = MODE_ADD;
meillo@120	3068 [...]
meillo@121	3069 case DELETESW: /* delete annotations */
meillo@121	3070 mode = MODE_DEL;
meillo@121	3071 continue;
meillo@121	3072 case LISTSW: /* produce a listing */
meillo@121	3073 mode = MODE_LIST;
meillo@121	3074 continue;
meillo@120	3075 VE
meillo@120	3076 .LP
meillo@121	3077 The replacement code does not only reflect the problem's structure better,
meillo@121	3078 it is easier to understand as well.
meillo@121	3079 The same applies to the documentation.
meillo@120	3080 The man page was completely reorganized to propagate the same structure.
meillo@121	3081 This is visible in the Synopsis section:
meillo@120	3082 .VS
meillo@120	3083 anno [+folder] [msgs] [-component field] [-text body]
meillo@120	3084 [-append] [-date \| -nodate] [-preserve \| -nopreserve]
meillo@120	3085 [-Version] [-help]
meillo@120	3086
meillo@120	3087 anno -delete [+folder] [msgs] [-component field] [-text
meillo@120	3088 body] [-number num \| all ] [-preserve \| -nopreserve]
meillo@120	3089 [-Version] [-help]
meillo@120	3090
meillo@120	3091 anno -list [+folder] [msgs] [-component field] [-number]
meillo@120	3092 [-Version] [-help]
meillo@120	3093 VE
meillo@121	3094 .\" XXX think about explaining the -preserve rework?
meillo@118	3095
meillo@58	3096
meillo@58	3097
meillo@133	3098 .U3 "Path Conversion
meillo@133	3099 .P
meillo@134	3100 Four kinds of path names can appear in MH:
meillo@134	3101 .IP (1)
meillo@134	3102 Absolute Unix directory paths, like
meillo@134	3103 .Fn /etc/passwd .
meillo@134	3104 .IP (2)
meillo@134	3105 Relative Unix directory paths, like
meillo@134	3106 .Fn ./foo/bar .
meillo@134	3107 .IP (3)
meillo@134	3108 Absolute MH folder paths, like
meillo@134	3109 .Fn +friends/phil .
meillo@134	3110 .IP (4)
meillo@134	3111 Relative MH folder paths, like
meillo@134	3112 .Fn @subfolder .
meillo@134	3113 .P
meillo@134	3114 The last type, relative MH folder paths, are hardly documented.
meillo@134	3115 Nonetheless, they are useful for large mail storages.
meillo@134	3116 The current mail folder is specified as `\c
meillo@134	3117 .Fn @ ',
meillo@134	3118 just like the current directory is specified as `\c
meillo@134	3119 .Fn . '.
meillo@134	3120 .P
meillo@134	3121 To allow MH tools to understand all four notations,
meillo@134	3122 they need to convert between them.
meillo@134	3123 In nmh, these path name conversion functions were located in the files
meillo@134	3124 .Fn sbr/path.c
meillo@134	3125 (``return a pathname'') and
meillo@134	3126 .Fn sbr/m_maildir.c
meillo@134	3127 (``get the path for the mail directory'').
meillo@134	3128 The seven functions in the two files were documented with no more
meillo@134	3129 than two comments, which described obvious information.
meillo@134	3130 The function signatures were neither explaining:
meillo@134	3131 .VS
meillo@134	3132 char path(char , int);
meillo@134	3133 char pluspath(char );
meillo@134	3134 char m_mailpath(char );
meillo@134	3135 char m_maildir(char );
meillo@134	3136 VE
meillo@134	3137 .P
meillo@134	3138 My investigation provides the following description:
meillo@134	3139 .BU
meillo@134	3140 The second parameter of
meillo@134	3141 .Fu path()
meillo@134	3142 defines the type of path given as first parameter.
meillo@134	3143 Directory paths are converted to absolute directory paths.
meillo@134	3144 Folder paths are converted to absolute folder paths.
meillo@134	3145 Folder paths must not include a leading `@' character.
meillo@134	3146 Leading plus characters are preserved.
meillo@134	3147 The result is a pointer to newly allocated memory.
meillo@134	3148 .BU
meillo@134	3149 .Fu pluspath()
meillo@134	3150 is a convenience-wrapper to
meillo@134	3151 .Fu path() ,
meillo@134	3152 to convert folder paths only.
meillo@134	3153 This function can not be used for directory paths.
meillo@134	3154 An empty string parameter causes a buffer overflow.
meillo@134	3155 .BU
meillo@134	3156 .Fu m_mailpath()
meillo@134	3157 converts directory paths to absolute directory paths.
meillo@134	3158 The characters `+' or `@' at the beginning of the path name are
meillo@134	3159 treated literal, i.e. as the first character of a relative directory path.
meillo@134	3160 Hence, this function can not be used for folder paths.
meillo@134	3161 In any case, the result is an absolute directory path.
meillo@134	3162 The result is a pointer to newly allocated memory.
meillo@134	3163 .BU
meillo@134	3164 .Fu m_maildir()
meillo@134	3165 returns the parameter unchanged if it is an absolute directory path
meillo@134	3166 or begins with the entry `.' or `..'.
meillo@134	3167 All other strings are prepended with the current working directory.
meillo@134	3168 Hence, this functions can not be used for folder paths.
meillo@134	3169 The result is either an absolute directory path or a relative
meillo@134	3170 directory path, starting with a dot.
meillo@134	3171 In contrast to the other functions, the result is a pointer to
meillo@134	3172 static memory.
meillo@134	3173 .P
meillo@134	3174 The situation was obscure, irritating, error-prone, and non-orthogonal.
meillo@134	3175 No clear terminology was used to name the different kinds of path names.
meillo@134	3176 The first argument of
meillo@134	3177 .Fu m_mailpath() ,
meillo@134	3178 for instance, was named
meillo@134	3179 .Ar folder ,
meillo@134	3180 though
meillo@134	3181 .Fu m_mailpath()
meillo@134	3182 can not be used for MH folders.
meillo@134	3183 .P
meillo@134	3184 I reworked the path name conversion completely, introducing clarity.
meillo@134	3185 First of all, the terminology needed to be defined.
meillo@134	3186 A path name is either in the Unix domain, then it is called
meillo@134	3187 \fIdirectory path\fP, `dirpath' for short, or it is in the MH domain,
meillo@134	3188 then it is called \fIfolder path\fP, `folpath' for short.
meillo@134	3189 The two terms need to be used with strict distinction.
meillo@134	3190 Having a clear terminology is often an indicator of having understood
meillo@134	3191 the problem itself.
meillo@134	3192 Second, I exploited the concept of path type indicators.
meillo@134	3193 By requesting every path name to start with a clear type identifier,
meillo@134	3194 conversion between the types can be fully automated.
meillo@134	3195 Thus the tools can accept paths of any type from the user.
meillo@134	3196 Therefore, it was necessary to require relative directory paths to be
meillo@134	3197 prefixed with a dot character.
meillo@134	3198 In consequence, the dot character could no longer be an alias for the
meillo@134	3199 current message.
meillo@134	3200 .Ci cff0e16925e7edbd25b8b9d6d4fbdf03e0e60c01
meillo@134	3201 Third, I created three new functions to replace the previous mess:
meillo@134	3202 .BU
meillo@134	3203 .Fu expandfol()
meillo@134	3204 converts folder paths to absolute folder paths,
meillo@134	3205 without the leading plus character.
meillo@134	3206 Directory paths are simply passed through.
meillo@134	3207 This function is to be used for folder paths only, thus the name.
meillo@134	3208 The result is a pointer to static memory.
meillo@134	3209 .BU
meillo@134	3210 .Fu expanddir()
meillo@134	3211 converts directory paths to absolute directory paths.
meillo@134	3212 Folder paths are treated as relative directory paths.
meillo@134	3213 This function is to be used for directory paths only, thus the name.
meillo@134	3214 The result is a pointer to static memory.
meillo@134	3215 .BU
meillo@134	3216 .Fu toabsdir()
meillo@134	3217 converts any type of path to an absolute directory path.
meillo@134	3218 This is the function of choice for path conversion.
meillo@134	3219 Absolute directory paths are the most general representation of a
meillo@134	3220 path name.
meillo@134	3221 The result is a pointer to static memory.
meillo@134	3222 .P
meillo@134	3223 The new functions have names that indicate their use.
meillo@134	3224 Two of the functions convert relative to absolute path names of the
meillo@134	3225 same type.
meillo@134	3226 The third function converts any path name type to the most general one,
meillo@134	3227 the absolute directory path.
meillo@134	3228 All of the functions return pointers to static memory.
meillo@134	3229 All three functions are implemented in
meillo@134	3230 .Fn sbr/path.c .
meillo@134	3231 .Fn sbr/m_maildir.c
meillo@134	3232 is removed.
meillo@134	3233 .P
meillo@134	3234 Along with the path conversion rework, I also replaced
meillo@134	3235 .Fu getfolder(FDEF)
meillo@134	3236 with
meillo@134	3237 .Fu getdeffol()
meillo@134	3238 and
meillo@134	3239 .Fu getfolder(FCUR)
meillo@134	3240 with
meillo@134	3241 .Fu getcurfol() ,
meillo@134	3242 which is only a convenience wrapper for
meillo@134	3243 .Fu expandfol("@") .
meillo@134	3244 This code was moved from
meillo@134	3245 .Fn sbr/getfolder.c
meillo@134	3246 to
meillo@134	3247 .Fn sbr/path.c .
meillo@134	3248 .P
meillo@134	3249 The related function
meillo@134	3250 .Fu etcpath()
meillo@134	3251 was moved to
meillo@134	3252 .Fn sbr/path.c ,
meillo@134	3253 too.
meillo@134	3254 Previously, it had been located in
meillo@134	3255 .Fn config/config.c ,
meillo@134	3256 for whatever reasons.
meillo@134	3257 .P
meillo@134	3258 .Fn sbr/path.c
meillo@134	3259 now contains all path handling code.
meillo@134	3260 Only 173 lines of code were needed to replace the previous 252 lines.
meillo@134	3261 The readability of the code is highly improved.
meillo@134	3262 Additionally, each of the six exported and one static functions
meillo@134	3263 is introduced by an explaining comment.
meillo@134	3264 .Ci d39e2c447b0d163a5a63f480b23d06edb7a73aa0
meillo@133	3265
meillo@133	3266
meillo@133	3267
meillo@133	3268
meillo@133	3269 .H2 "Profile Reading
meillo@133	3270 .P
meillo@133	3271 FIXME XXX
meillo@133	3272
meillo@133	3273 commit 3e017a7abbdf69bf0dff7a4073275961eda1ded8
meillo@133	3274 Author: markus schnalke <meillo@marmaro.de>
meillo@133	3275 Date: Wed Jun 27 14:23:35 2012 +0200
meillo@133	3276
meillo@133	3277 spost: Read profile and context now. Removed -library switch.
meillo@133	3278 spost is a full part of the mmh toolchest, hence, it shall read the
meillo@133	3279 profile/context. This will remove the need to pass profile information
meillo@133	3280 from send to spost via command line switches.
meillo@133	3281 In January 2012, there had been a discussion on the nmh-workers ML
meillo@133	3282 whether post should read the profile/context. There wasn't a clear
meillo@133	3283 answer. It behavior was mainly motivated by the historic situation,
meillo@133	3284 it seems. My opinion on the topic goes into the direction that every
meillo@133	3285 tool that is part of the mmh toolchest should read the profile. That
meillo@133	3286 is a clear and simple concept. Using MH tools without wanting to
meillo@133	3287 interact with MH (like mhmail had been) is no more a practical problem.
meillo@133	3288
meillo@133	3289 commit 32d4f9daaa70519be3072479232ff7be0500d009
meillo@133	3290 Author: markus schnalke <meillo@marmaro.de>
meillo@133	3291 Date: Wed Jun 27 13:15:47 2012 +0200
meillo@133	3292
meillo@133	3293 mhmail: Read the context!
meillo@133	3294 mhmail will change from a mailx-replacment to an alternative to
meillo@133	3295 `comp -ed prompter', thus being a send front-end. Hence, mhmail
meillo@133	3296 should not stay outside the profile/context respecting mmh toolchest.
meillo@133	3297
meillo@133	3298
meillo@133	3299 slocal
meillo@133	3300
meillo@133	3301
meillo@133	3302
meillo@127	3303
meillo@121	3304 .H2 "Standard Libraries
meillo@22	3305 .P
meillo@121	3306 MH is one decade older than the POSIX and ANSI C standards.
meillo@121	3307 Hence, MH included own implementations of functions
meillo@121	3308 that are standardized and thus widely available today,
meillo@121	3309 but were not back then.
meillo@121	3310 Today, twenty years after the POSIX and ANSI C were published,
meillo@121	3311 developers can expect system to comply with these standards.
meillo@121	3312 In consequence, MH-specific replacements for standard functions
meillo@121	3313 can and should be dropped.
meillo@121	3314 Kernighan and Pike advise: ``Use standard libraries.''
meillo@121	3315 .[ [
meillo@121	3316 kernighan pike practice of programming
meillo@121	3317 .], p. 196]
meillo@121	3318 Actually, MH had followed this advice in history,
meillo@121	3319 but it had not adjusted to the changes in this field.
meillo@121	3320 The
meillo@121	3321 .Fu snprintf()
meillo@121	3322 function, for instance, was standardized with C99 and is available
meillo@121	3323 almost everywhere because of its high usefulness.
meillo@123	3324 In project's own implementation of
meillo@121	3325 .Fu snprintf()
meillo@123	3326 was dropped in March 2012 in favor for using the one of the
meillo@123	3327 standard library.
meillo@123	3328 .Ci 0052f1024deb0a0a2fc2e5bacf93d45a5a9c9b32
meillo@123	3329 Such decisions limit the portability of mmh
meillo@121	3330 if systems don't support these standardized and widespread functions.
meillo@123	3331 This compromise is made because mmh focuses on the future.
meillo@121	3332 .P
meillo@123	3333 I am not yet thirty years old and my C and Unix experience comprises
meillo@123	3334 only half a dozen years.
meillo@121	3335 Hence, I need to learn about the history in retrospective.
meillo@121	3336 I have not used those ancient constructs myself.
meillo@121	3337 I have not suffered from their incompatibilities.
meillo@121	3338 I have not longed for standardization.
meillo@121	3339 All my programming experience is from a time when ANSI C and POSIX
meillo@121	3340 were well established already.
meillo@121	3341 I have only read a lot of books about the (good) old times.
meillo@121	3342 This puts me in a difficult positions when working with old code.
meillo@123	3343 I need to freshly acquire knowledge about old code constructs and ancient
meillo@123	3344 programming styles, whereas older programmers know these things by
meillo@123	3345 heart from their own experience.
meillo@121	3346 .P
meillo@123	3347 Being aware of the situation, I rather let people with more historic
meillo@123	3348 experience replace ancient code constructs with standardized ones.
meillo@121	3349 Lyndon Nerenberg covered large parts of this task for the nmh project.
meillo@121	3350 He converted project-specific functions to POSIX replacements,
meillo@121	3351 also removing the conditionals compilation of now standardized features.
meillo@123	3352 Ken Hornstein and David Levine had their part in the work, too.
meillo@121	3353 Often, I only needed to pull over changes from nmh into mmh.
meillo@121	3354 These changes include many commits; these are among them:
meillo@121	3355 .Ci 768b5edd9623b7238e12ec8dfc409b82a1ed9e2d
meillo@121	3356 .Ci 0052f1024deb0a0a2fc2e5bacf93d45a5a9c9b32 .
meillo@102	3357 .P
meillo@123	3358 During my own work, I tidied up the \fIMH standard library\fP,
meillo@123	3359 .Fn libmh.a ,
meillo@123	3360 which is located in the
meillo@123	3361 .Fn sbr
meillo@123	3362 (``subroutines'') directory in the source tree.
meillo@123	3363 The MH library includes functions that mmh tools usually need.
meillo@123	3364 Among them are MH-specific functions for profile, context, sequence,
meillo@123	3365 and folder handling, but as well
meillo@123	3366 MH-independent functions, such as auxiliary string functions,
meillo@123	3367 portability interfaces and error-checking wrappers for critical
meillo@123	3368 functions of the standard library.
meillo@123	3369 .P
meillo@123	3370 I have replaced the
meillo@121	3371 .Fu atooi()
meillo@121	3372 function with calls to
meillo@123	3373 .Fu strtoul()
meillo@121	3374 with the third parameter \(en the base \(en set to eight.
meillo@121	3375 .Fu strtoul()
meillo@123	3376 is part of C89 and thus considered safe to use.
meillo@121	3377 .Ci c490c51b3c0f8871b6953bd0c74551404f840a74
meillo@102	3378 .P
meillo@121	3379 I did remove project-included fallback implementations of
meillo@121	3380 .Fu memmove()
meillo@121	3381 and
meillo@121	3382 .Fu strerror() ,
meillo@121	3383 although Peter Maydell had re-included them into nmh in 2008
meillo@121	3384 to support SunOS 4.
meillo@121	3385 Nevertheless, these functions are part of ANSI C.
meillo@121	3386 Systems that do not even provide full ANSI C support should not
meillo@121	3387 put a load on mmh.
meillo@121	3388 .Ci b067ff5c465a5d243ce5a19e562085a9a1a97215
meillo@121	3389 .P
meillo@121	3390 The
meillo@121	3391 .Fu copy()
meillo@121	3392 function copies the string in argument one to the location in two.
meillo@121	3393 In contrast to
meillo@121	3394 .Fu strcpy() ,
meillo@121	3395 it returns a pointer to the terminating null-byte in the destination area.
meillo@123	3396 The code was adjusted to replace
meillo@121	3397 .Fu copy()
meillo@123	3398 with
meillo@121	3399 .Fu strcpy() ,
meillo@121	3400 except within
meillo@121	3401 .Fu concat() ,
meillo@121	3402 where
meillo@121	3403 .Fu copy()
meillo@123	3404 was more convenient.
meillo@123	3405 Therefore, the definition of
meillo@121	3406 .Fu copy()
meillo@123	3407 was moved into the source file of
meillo@121	3408 .Fu concat()
meillo@123	3409 and its visibility is now limited to it.
meillo@121	3410 .Ci 552fd7253e5ee9e554c5c7a8248a6322aa4363bb
meillo@121	3411 .P
meillo@121	3412 The function
meillo@121	3413 .Fu r1bindex()
meillo@121	3414 had been a generalized version of
meillo@121	3415 .Fu basename()
meillo@121	3416 with minor differences.
meillo@121	3417 As all calls to
meillo@121	3418 .Fu r1bindex()
meillo@121	3419 had the slash (`/') as delimiter anyway,
meillo@121	3420 replacing
meillo@121	3421 .Fu r1bindex()
meillo@121	3422 with the more specific and better-named function
meillo@121	3423 .Fu basename()
meillo@121	3424 became desirable.
meillo@121	3425 Unfortunately, many of the 54 calls to
meillo@121	3426 .Fu r1bindex()
meillo@123	3427 depended on a special behavior,
meillo@121	3428 which differed from the POSIX specification for
meillo@121	3429 .Fu basename() .
meillo@121	3430 Hence,
meillo@121	3431 .Fu r1bindex()
meillo@121	3432 was kept but renamed to
meillo@123	3433 .Fu mhbasename() ,
meillo@123	3434 fixing the delimiter to the slash.
meillo@121	3435 .Ci 240013872c392fe644bd4f79382d9f5314b4ea60
meillo@121	3436 For possible uses of
meillo@121	3437 .Fu r1bindex()
meillo@121	3438 with a different delimiter,
meillo@121	3439 the ANSI C function
meillo@121	3440 .Fu strrchr()
meillo@121	3441 provides the core functionality.
meillo@121	3442 .P
meillo@121	3443 The
meillo@121	3444 .Fu ssequal()
meillo@121	3445 function \(en apparently for ``substring equal'' \(en
meillo@121	3446 was renamed to
meillo@121	3447 .Fu isprefix() ,
meillo@121	3448 because this is what it actually checks.
meillo@121	3449 .Ci c20b4fa14515c7ab388ce35411d89a7a92300711
meillo@121	3450 Its source file had included the following comments, no joke.
meillo@121	3451 .VS
meillo@121	3452 /*
meillo@121	3453 * THIS CODE DOES NOT WORK AS ADVERTISED.
meillo@121	3454 * It is actually checking if s1 is a PREFIX of s2.
meillo@121	3455 * All calls to this function need to be checked to see
meillo@121	3456 * if that needs to be changed. Prefix checking is cheaper, so
meillo@121	3457 * should be kept if it's sufficient.
meillo@121	3458 */
meillo@121	3459
meillo@121	3460 /*
meillo@121	3461 * Check if s1 is a substring of s2.
meillo@121	3462 * If yes, then return 1, else return 0.
meillo@121	3463 */
meillo@121	3464 VE
meillo@123	3465 Two months later, it was completely removed by replacing it with
meillo@123	3466 .Fu strncmp() .
meillo@123	3467 .Ci b0b1dd37ff515578cf7cba51625189eb34a196cb
meillo@121	3468
meillo@102	3469
meillo@102	3470
meillo@102	3471
meillo@133	3472
meillo@133	3473 .H2 "User Data Locations
meillo@133	3474 .P
meillo@133	3475 In nmh, a personal setup consists of the MH profile and the MH directory.
meillo@133	3476 The profile is a file named
meillo@133	3477 .Fn \&.mh_profile
meillo@133	3478 in the user's home directory.
meillo@133	3479 It contains the static configuration.
meillo@133	3480 It also contains the location of the MH directory in the profile entry
meillo@133	3481 .Pe Path .
meillo@133	3482 The MH directory contains the mail storage and is the first
meillo@133	3483 place to search for personal forms, scan formats, and similar
meillo@133	3484 configuration files.
meillo@133	3485 The location of the MH directory can be chosen freely by the user.
meillo@133	3486 The default and usual name is a directory named
meillo@133	3487 .Fn Mail
meillo@133	3488 in the home directory.
meillo@133	3489 .P
meillo@133	3490 The way MH data is splitted between profile and MH directory is a legacy.
meillo@133	3491 It is only sensible in a situation where the profile is the only
meillo@133	3492 configuration file.
meillo@133	3493 Why else should the mail storage and the configuration files be intermixed?
meillo@133	3494 They are different kinds of data:
meillo@133	3495 The data to be operated on and the configuration to change how
meillo@133	3496 tools operate.
meillo@133	3497 Splitting the configuration between the profile and the MH directory
meillo@133	3498 is bad.
meillo@133	3499 Merging the mail storage and the configuration in one directory is bad
meillo@133	3500 as well.
meillo@133	3501 As the mail storage and the configuration were not separated sensibly
meillo@133	3502 in the first place, I did it now.
meillo@133	3503 .P
meillo@133	3504 Personal mmh data is grouped by type, resulting in two distinct parts:
meillo@133	3505 The mail storage and the configuration.
meillo@133	3506 In mmh, the mail storage directory still contains all the messages,
meillo@133	3507 but, in exception of public sequences files, nothing else.
meillo@133	3508 In difference to nmh, the auxiliary configuration files are no longer
meillo@133	3509 located there.
meillo@133	3510 Therefore, the directory is no longer called the user's \fIMH directory\fP
meillo@133	3511 but his \fImail storage\fP.
meillo@133	3512 Its location is still user-chosen, with the default name
meillo@133	3513 .Fn Mail ,
meillo@133	3514 in the user's home directory.
meillo@133	3515 In mmh, the configuration is grouped together in
meillo@133	3516 the hidden directory
meillo@133	3517 .Fn \&.mmh
meillo@133	3518 in the user's home directory.
meillo@133	3519 This \fImmh directory\fP contains the context file, personal forms,
meillo@133	3520 scan formats, and the like, but also the user's profile, now named
meillo@133	3521 .Fn profile .
meillo@133	3522 The location of the profile is no longer fixed to
meillo@133	3523 .Fn $HOME/.mh_profile
meillo@133	3524 but to
meillo@133	3525 .Fn $HOME/.mmh/profile .
meillo@133	3526 Having both, the file
meillo@133	3527 .Fn $HOME/.mh_profile
meillo@133	3528 and the configuration directory
meillo@133	3529 .Fn $HOME/.mmh
meillo@133	3530 appeared to be inconsistent.
meillo@133	3531 The approach chosen for mmh is consistent, simple, and familiar to
meillo@133	3532 Unix users.
meillo@133	3533 .P
meillo@133	3534 MH allows users to have multiiple MH setups.
meillo@133	3535 Therefore, it is necessary to select a different profile.
meillo@133	3536 The profile is the single entry point to access the rest of a
meillo@133	3537 personal MH setup.
meillo@133	3538 In nmh, the environment variable
meillo@133	3539 .Ev MH
meillo@133	3540 could be used to specifiy a different profile.
meillo@133	3541 To operate in the same MH setup with a separate context,
meillo@133	3542 the
meillo@133	3543 .Ev MHCONTEXT
meillo@133	3544 environment variable could be used.
meillo@133	3545 This allows having own current folders and current messages in
meillo@133	3546 each terminal, for instance.
meillo@133	3547 In mmh, three environment variables are used.
meillo@133	3548 .Ev MMH
meillo@133	3549 overrides the default location of the mmh directory (\c
meillo@133	3550 .Fn .mmh ).
meillo@133	3551 .Ev MMHP
meillo@133	3552 and
meillo@133	3553 .Ev MMHC
meillo@133	3554 override the paths to the profile and context files, respectively.
meillo@133	3555 This approach allows the set of personal configuration files to be chosen
meillo@133	3556 independently from the profile, context, and mail storage.
meillo@133	3557 .P
meillo@133	3558 The separation of the files by type is sensible and convenient.
meillo@133	3559 The new approach has no functional disadvantages,
meillo@133	3560 as every setup I can imagine can be implemented with both approaches,
meillo@133	3561 possibly even easier with the new approach.
meillo@133	3562 The main achievement of the change is the clear and sensible split
meillo@133	3563 between mail storage and configuration.
meillo@133	3564
meillo@133	3565
meillo@133	3566
meillo@133	3567
meillo@133	3568
meillo@118	3569 .H2 "Modularization
meillo@118	3570 .P
meillo@123	3571 The source code of the mmh tools is located in the
meillo@122	3572 .Fn uip
meillo@123	3573 (``user interface programs'') directory.
meillo@123	3574 Each tools has a source file with the same name.
meillo@122	3575 For example,
meillo@122	3576 .Pn rmm
meillo@122	3577 is built from
meillo@122	3578 .Fn uip/rmm.c .
meillo@123	3579 Some source files are used for multiple programs.
meillo@122	3580 For example
meillo@122	3581 .Fn uip/scansbr.c
meillo@123	3582 is used for both,
meillo@122	3583 .Pn scan
meillo@122	3584 and
meillo@122	3585 .Pn inc .
meillo@122	3586 In nmh, 49 tools were built from 76 source files.
meillo@123	3587 This is a ratio of 1.6 source files per program.
meillo@123	3588 32 programs depended on multiple source files;
meillo@123	3589 17 programs depended on one source file only.
meillo@122	3590 In mmh, 39 tools are built from 51 source files.
meillo@123	3591 This is a ratio of 1.3 source files per program.
meillo@123	3592 18 programs depend on multiple source files;
meillo@123	3593 21 programs depend on one source file only.
meillo@123	3594 (These numbers and the ones in the following text ignore the MH library
meillo@123	3595 as well as shell scripts and multiple names for the same program.)
meillo@122	3596 .P
meillo@123	3597 Splitting the source code of a large program into multiple files can
meillo@122	3598 increase the readability of its source code.
meillo@124	3599 Most of the mmh tools, however, are simple and straight-forward programs.
meillo@122	3600 With the exception of the MIME handling tools,
meillo@122	3601 .Pn pick
meillo@122	3602 is the largest tools.
meillo@122	3603 It contains 1\\|037 lines of source code (measured with
meillo@122	3604 .Pn sloccount ), excluding the MH library.
meillo@122	3605 Only the MIME handling tools (\c
meillo@122	3606 .Pn mhbuild ,
meillo@122	3607 .Pn mhstore ,
meillo@122	3608 .Pn show ,
meillo@122	3609 etc.)
meillo@122	3610 are larger.
meillo@122	3611 Splitting programs with less than 1\\|000 lines of code into multiple
meillo@123	3612 source files seldom leads to better readability.
meillo@123	3613 For such tools, splitting makes sense
meillo@122	3614 when parts of the code are reused in other programs,
meillo@122	3615 and the reused code fragment is not general enough
meillo@122	3616 for including it in the MH library,
meillo@124	3617 or, if the code has dependencies on a library that only few programs need.
meillo@122	3618 .Fn uip/packsbr.c ,
meillo@122	3619 for instance, provides the core program logic for the
meillo@122	3620 .Pn packf
meillo@122	3621 and
meillo@122	3622 .Pn rcvpack
meillo@122	3623 programs.
meillo@122	3624 .Fn uip/packf.c
meillo@122	3625 and
meillo@122	3626 .Fn uip/rcvpack.c
meillo@122	3627 mainly wrap the core function appropriately.
meillo@122	3628 No other tools use the folder packing functions.
meillo@123	3629 As another example,
meillo@123	3630 .Fn uip/termsbr.c
meillo@123	3631 provides termcap support, which requires linking with a termcap or
meillo@123	3632 curses library.
meillo@123	3633 Including
meillo@123	3634 .Fn uip/termsbr.c
meillo@123	3635 into the MH library would require every program to be linked with
meillo@123	3636 termcap or curses, although only few of the programs require it.
meillo@122	3637 .P
meillo@122	3638 The task of MIME handling is complex enough that splitting its code
meillo@122	3639 into multiple source files improves the readability.
meillo@122	3640 The program
meillo@122	3641 .Pn mhstore ,
meillo@122	3642 for instance, is compiled out of seven source files with 2\\|500
meillo@122	3643 lines of code in summary.
meillo@122	3644 The main code file
meillo@122	3645 .Fn uip/mhstore.c
meillo@123	3646 consists of 800 lines; the other 1\\|700 lines of code are reused in
meillo@123	3647 other MIME handling tools.
meillo@123	3648 It seems to be worthwhile to bundle the generic MIME handling code into
meillo@123	3649 a MH-MIME library, as a companion to the MH standard library.
meillo@122	3650 This is left open for the future.
meillo@122	3651 .P
meillo@123	3652 The work already done, focussed on the non-MIME tools.
meillo@122	3653 The amount of code compiled into each program was reduced.
meillo@123	3654 This eases the understanding of the code base.
meillo@122	3655 In nmh,
meillo@122	3656 .Pn comp
meillo@122	3657 was built from six source files:
meillo@122	3658 .Fn comp.c ,
meillo@122	3659 .Fn whatnowproc.c ,
meillo@122	3660 .Fn whatnowsbr.c ,
meillo@122	3661 .Fn sendsbr.c ,
meillo@122	3662 .Fn annosbr.c ,
meillo@122	3663 and
meillo@122	3664 .Fn distsbr.c .
meillo@122	3665 In mmh, it builds from only two:
meillo@122	3666 .Fn comp.c
meillo@122	3667 and
meillo@122	3668 .Fn whatnowproc.c .
meillo@123	3669 In nmh's
meillo@123	3670 .Pn comp ,
meillo@123	3671 the core function of
meillo@122	3672 .Pn whatnow ,
meillo@122	3673 .Pn send ,
meillo@122	3674 and
meillo@122	3675 .Pn anno
meillo@123	3676 were compiled into
meillo@122	3677 .Pn comp .
meillo@123	3678 This saved the need to execute these programs with
meillo@122	3679 .Fu fork()
meillo@122	3680 and
meillo@122	3681 .Fu exec() ,
meillo@122	3682 two expensive system calls.
meillo@122	3683 Whereis this approach improved the time performance,
meillo@122	3684 it interweaved the source code.
meillo@122	3685 Core functionalities were not encapsulated into programs but into
meillo@122	3686 function, which were then wrapped by programs.
meillo@122	3687 For example,
meillo@122	3688 .Fn uip/annosbr.c
meillo@122	3689 included the function
meillo@122	3690 .Fu annotate() .
meillo@122	3691 Each program that wanted to annotate messages, included the source file
meillo@123	3692 .Fn uip/annosbr.c
meillo@123	3693 and called
meillo@123	3694 .Fu annotate() .
meillo@123	3695 Because the function
meillo@123	3696 .Fu annotate()
meillo@123	3697 was used like the tool
meillo@123	3698 .Pn anno ,
meillo@123	3699 it had seven parameters, reflecting the command line switches of the tool.
meillo@122	3700 When another pair of command line switches was added to
meillo@122	3701 .Pn anno ,
meillo@122	3702 a rather ugly hack was implemented to avoid adding another parameter
meillo@122	3703 to the function.
meillo@122	3704 .Ci d9b1d57351d104d7ec1a5621f090657dcce8cb7f
meillo@122	3705 .P
meillo@122	3706 Separation simplifies the understanding of program code
meillo@122	3707 because the area influenced by any particular statement is smaller.
meillo@122	3708 The separating on the program-level is more strict than the separation
meillo@122	3709 on the function level.
meillo@122	3710 In mmh, the relevant code of
meillo@122	3711 .Pn comp
meillo@122	3712 comprises the two files
meillo@122	3713 .Fn uip/comp.c
meillo@122	3714 and
meillo@122	3715 .Fn uip/whatnowproc.c ,
meillo@123	3716 together 210 lines of code.
meillo@122	3717 In nmh,
meillo@122	3718 .Pn comp
meillo@122	3719 comprises six files with 2\\|450 lines.
meillo@123	3720 Not all of the code in these six files was actually used by
meillo@122	3721 .Pn comp ,
meillo@123	3722 but the code reader needed to read all of the code first to know which
meillo@123	3723 parts were used.
meillo@122	3724 .P
meillo@123	3725 As I have read a lot in the code base during the last two years,
meillo@123	3726 I learned about the easy and the difficult parts.
meillo@123	3727 Code is easy to understand if:
meillo@123	3728 .BU
meillo@123	3729 The influenced code area is small
meillo@123	3730 .BU
meillo@124	3731 The boundaries are strictly defined
meillo@123	3732 .BU
meillo@123	3733 The code is written straight-forward
meillo@123	3734 .P
meillo@123	3735 .\" XXX move this paragraph somewhere else?
meillo@123	3736 Reading
meillo@122	3737 .Pn rmm 's
meillo@122	3738 source code in
meillo@122	3739 .Fn uip/rmm.c
meillo@122	3740 is my recommendation for a beginner's entry point into the code base of nmh.
meillo@122	3741 The reasons are that the task of
meillo@122	3742 .Pn rmm
meillo@122	3743 is straight forward and it consists of one small source code file only,
meillo@122	3744 yet its source includes code constructs typical for MH tools.
meillo@122	3745 With the introduction of the trash folder in mmh,
meillo@122	3746 .Pn rmm
meillo@122	3747 became a bit more complex, because it invokes
meillo@122	3748 .Pn refile .
meillo@122	3749 Still, it is a good example for a simple tool with clear sources.
meillo@122	3750 .P
meillo@122	3751 Understanding
meillo@122	3752 .Pn comp
meillo@122	3753 requires to read 210 lines of code in mmh, but ten times as much in nmh.
meillo@123	3754 Due to the aforementioned hack in
meillo@122	3755 .Pn anno
meillo@122	3756 to save the additional parameter, information passed through the program's
meillo@122	3757 source base in obscure ways.
meillo@123	3758 Thus, understanding
meillo@122	3759 .Pn comp ,
meillo@123	3760 required understanding the inner workings of
meillo@122	3761 .Fn uip/annosbr.c
meillo@122	3762 first.
meillo@123	3763 To be sure to fully understand a program, its whole source code needs
meillo@122	3764 to be examined.
meillo@123	3765 Not doing so is a leap of faith, assuming that the developers
meillo@122	3766 have avoided obscure programming techniques.
meillo@122	3767 By separating the tools on the program-level, the boundaries are
meillo@122	3768 clearly visible and technically enforced.
meillo@122	3769 The interfaces are calls to
meillo@122	3770 .Fu exec()
meillo@122	3771 rather than arbitrary function calls.
meillo@123	3772 .P
meillo@123	3773 But the real problem is another:
meillo@123	3774 Nmh violates the golden ``one tool, one job'' rule of the Unix philosophy.
meillo@123	3775 Understanding
meillo@122	3776 .Pn comp
meillo@123	3777 requires understanding
meillo@123	3778 .Fn uip/annosbr.c
meillo@123	3779 and
meillo@123	3780 .Fn uip/sendsbr.c
meillo@123	3781 because
meillo@123	3782 .Pn comp
meillo@123	3783 does annotate and send messages.
meillo@123	3784 In nmh, there surely exists the tool
meillo@122	3785 .Pn send ,
meillo@123	3786 which does (almost) only send messages.
meillo@123	3787 But
meillo@122	3788 .Pn comp
meillo@123	3789 and
meillo@122	3790 .Pn repl
meillo@122	3791 and
meillo@122	3792 .Pn forw
meillo@122	3793 and
meillo@122	3794 .Pn dist
meillo@122	3795 and
meillo@122	3796 .Pn whatnow
meillo@122	3797 and
meillo@123	3798 .Pn viamail ,
meillo@123	3799 they all (!) have the same message sending function included, too.
meillo@123	3800 In result,
meillo@123	3801 .Pn comp
meillo@123	3802 sends messages without using
meillo@123	3803 .Pn send .
meillo@123	3804 The situation is the same as if
meillo@123	3805 .Pn grep
meillo@123	3806 would page without
meillo@123	3807 .Pn more
meillo@123	3808 just because both programs are part of the same code base.
meillo@123	3809 .P
meillo@122	3810 The clear separation on the surface \(en the toolchest approach \(en
meillo@123	3811 is violated on the level below.
meillo@122	3812 This violation is for the sake of time performance.
meillo@122	3813 On systems where
meillo@122	3814 .Fu fork()
meillo@122	3815 and
meillo@122	3816 .Fu exec()
meillo@122	3817 are expensive, the quicker response might be noticable.
meillo@124	3818 In the old times, sacrificing readability and conceptional beauty for
meillo@124	3819 speed might even have been a must to prevent MH from being unusably slow.
meillo@122	3820 Whatever the reasons had been, today they are gone.
meillo@123	3821 No longer should we sacrifice readability or conceptional beauty.
meillo@122	3822 No longer should we violate the Unix philosophy's ``one tool, one job''
meillo@122	3823 guideline.
meillo@123	3824 No longer should we keep speed improvements that became unnecessary.
meillo@122	3825 .P
meillo@123	3826 Therefore, mmh's
meillo@123	3827 .Pn comp
meillo@123	3828 does no longer send messages.
meillo@123	3829 In mmh, different jobs are divided among separate programs that
meillo@122	3830 invoke each other as needed.
meillo@123	3831 In consequence,
meillo@123	3832 .Pn comp
meillo@123	3833 invokes
meillo@123	3834 .Pn whatnow
meillo@123	3835 which thereafter invokes
meillo@123	3836 .Pn send .
meillo@123	3837 The clear separation on the surface is maintained on the level below.
meillo@123	3838 Human users and the tools use the same interface \(en
meillo@123	3839 annotations, for example, are made by invoking
meillo@123	3840 .Pn anno ,
meillo@123	3841 no matter if requested by programs or by human beings.
meillo@123	3842 The decrease of tools built from multiple source files and thus
meillo@123	3843 the decrease of
meillo@123	3844 .Fn uip/*sbr.c
meillo@123	3845 files confirm the improvement.
meillo@123	3846 .P
meillo@123	3847 One disadvantage needs to be taken with this change:
meillo@123	3848 The compiler can no longer check the integrity of the interfaces.
meillo@123	3849 By changing the command line interfaces of tools, it is
meillo@123	3850 the developer's job to adjust the invocations of these tools as well.
meillo@123	3851 As this is a manual task and regression tests, which could detect such
meillo@124	3852 problems, are not available yet, it is prone to errors.
meillo@123	3853 These errors will not be detected at compile time but at run time.
meillo@123	3854 Installing regression tests is a task left to do.
meillo@123	3855 In the best case, a uniform way of invoking tools from other tools
meillo@123	3856 can be developed to allow automated testing at compile time.