docs/master: discussion.roff annotate

docs/master

annotate discussion.roff @ 130:0b9aa74ced4d

Reworked the text on the Trash Folder.

author	markus schnalke <meillo@marmaro.de>
date	Mon, 02 Jul 2012 23:14:19 +0200
parents	01af3c0dfe7b
children	7c741bc8f719

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meillo@87	20 I believe that the development of all-in-one mail systems is obsolete.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