docs/master: discussion.roff annotate

docs/master

annotate discussion.roff @ 110:4c0f13b1e0e8

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author	markus schnalke <meillo@marmaro.de>
date	Sun, 24 Jun 2012 21:59:29 +0200
parents	2b094b8fb422
children	4e6a9ae1b53c

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@100	14 .H1 "Stream-Lining
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meillo@87	20 I believe that the development of all-in-one mail systems is obsolete.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@87	53 Peripheral parts should be removed to stream-line 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@100	272 By removing these tools, the project shall become more stream-lined
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@76	369 Removing them stream-lines 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@109	1641 The code base of mmh originates from the late seventies.
meillo@109	1642 Through the eighties, extensive work had been done on it.
meillo@109	1643 In the nineties, it was partly reorganized and extended.
meillo@102	1644 Relicts from each decade have gathered in the code base.
meillo@102	1645 My goal was to modernize the code base.
meillo@102	1646
meillo@102	1647 .P
meillo@102	1648 FIXME functional aspect only here
meillo@102	1649 .P
meillo@102	1650 FIXME ref to `code style' for non-functional aspects.
meillo@58	1651
meillo@58	1652
meillo@100	1653 .H2 "Code Relicts
meillo@0	1654 .P
meillo@109	1655 My position to drop obsolete functions of mmh, in order to remove old code,
meillo@104	1656 is much more revolutional than the nmh community likes to have it.
meillo@104	1657 Working on an experimental version, I was able to quickly drop
meillo@104	1658 functionality I considered ancient.
meillo@104	1659 The need for consensus with peers would have slowed this process down.
meillo@104	1660 Without the need to justify my decisions, I was able to rush forward.
meillo@110	1661 In December 2011, Paul Vixie motivated the nmh developers to just
meillo@104	1662 do the work:
meillo@104	1663 .[
meillo@104	1664 paul vixie edginess nmh-workers
meillo@104	1665 .]
meillo@104	1666 .QS
meillo@104	1667 let's stop walking on egg shells with this code base. there's no need to
meillo@104	1668 discuss whether to keep using vfork, just note in [sic!] passing, [...]
meillo@104	1669 we don't need a separate branch for removing vmh
meillo@104	1670 or ridding ourselves of #ifdef's or removing posix replacement functions
meillo@104	1671 or depending on pure ansi/posix "libc".
meillo@104	1672 .QP
meillo@104	1673 these things should each be a day or two of work and the "main branch"
meillo@104	1674 should just be modern. [...]
meillo@104	1675 let's push forward, aggressively.
meillo@104	1676 .QE
meillo@104	1677 .LP
meillo@104	1678 I did so already in the months before.
meillo@104	1679 I pushed forward.
meillo@104	1680 I simply dropped the cruft.
meillo@104	1681 .P
meillo@104	1682 The decision to drop a feature was based on literature research and
meillo@104	1683 careful thinking, but whether having had contact to this particular
meillo@104	1684 feature within my own computer life served as a rule of thumb.
meillo@109	1685 Always, I explained my reasons in the commit messages
meillo@109	1686 in the version control system.
meillo@104	1687 Hence, others can comprehend my view and argue for undoing the change
meillo@104	1688 if I have missed an important aspect.
meillo@109	1689 I was quick in dropping parts.
meillo@109	1690 I rather re-included falsely dropped parts than going a slower pace.
meillo@109	1691 Mmh is experimental work; it required tough decisions.
meillo@12	1692
meillo@102	1693
meillo@104	1694 .U3 "Forking
meillo@12	1695 .P
meillo@109	1696 Being a tool chest, MH creates many processes.
meillo@104	1697 In earlier times
meillo@104	1698 .Fu fork()
meillo@104	1699 had been an expensive system call, because the process's image needed
meillo@104	1700 to be duplicated completely at once.
meillo@109	1701 This was especially painful in the common case when the image gets
meillo@104	1702 replaced by a call to
meillo@104	1703 .Fu exec()
meillo@104	1704 right after having forked the child process.
meillo@104	1705 The
meillo@104	1706 .Fu vfork()
meillo@104	1707 system call was invented to speed up this particular case.
meillo@104	1708 It completely omits the duplication of the image.
meillo@104	1709 On old systems this resulted in significant speed ups.
meillo@104	1710 Therefore MH used
meillo@104	1711 .Fu vfork()
meillo@104	1712 whenever possible.
meillo@12	1713 .P
meillo@104	1714 Modern memory management units support copy-on-write semantics, which make
meillo@104	1715 .Fu fork()
meillo@104	1716 almost as fast as
meillo@104	1717 .Fu vfork() .
meillo@104	1718 The man page of
meillo@104	1719 .Mp vfork (2)
meillo@104	1720 in FreeBSD 8.0 states:
meillo@104	1721 .QS
meillo@104	1722 This system call will be eliminated when proper system sharing mechanisms
meillo@104	1723 are implemented. Users should not depend on the memory sharing semantics
meillo@104	1724 of vfork() as it will, in that case, be made synonymous to fork(2).
meillo@104	1725 .QE
meillo@104	1726 .LP
meillo@104	1727 Vixie supports the removal with the note that ``the last
meillo@104	1728 system on which fork was so slow that an mh user would notice it, was
meillo@104	1729 Eunice. that was 1987''.
meillo@104	1730 .[
meillo@104	1731 nmh-workers vixie edginess
meillo@104	1732 .]
meillo@104	1733 I replaced all calls to
meillo@104	1734 .Fu vfork()
meillo@104	1735 with calls to
meillo@104	1736 .Fu fork() .
meillo@109	1737 .Ci 40821f5c1316e9205a08375e7075909cc9968e7d
meillo@104	1738 .P
meillo@104	1739 Related to the costs of
meillo@104	1740 .Fu fork()
meillo@104	1741 is the probability of its success.
meillo@109	1742 In the eighties, on heavy loaded systems, calls to
meillo@104	1743 .Fu fork()
meillo@104	1744 were prone to failure.
meillo@104	1745 Hence, many of the
meillo@104	1746 .Fu fork()
meillo@104	1747 calls in the code were wrapped into loops to retry the
meillo@104	1748 .Fu fork()
meillo@109	1749 several times, to increase the changes to succeed, eventually.
meillo@109	1750 On modern systems, a failing
meillo@104	1751 .Fu fork()
meillo@109	1752 call is unusual.
meillo@104	1753 Hence, in the rare case when
meillo@104	1754 .Fu fork()
meillo@104	1755 fails, mmh programs simply abort.
meillo@109	1756 .Ci 5fbf37ee68e018998ada61eeab73e035b26834b6
meillo@12	1757
meillo@12	1758
meillo@109	1759 .U3 "Header Fields
meillo@104	1760 .BU
meillo@84	1761 The
meillo@84	1762 .Hd Encrypted
meillo@104	1763 header field was introduced by RFC\\|822,
meillo@109	1764 but already marked as legacy in RFC\\|2822.
meillo@109	1765 Today, OpenPGP provides the basis for standardized exchange of encrypted
meillo@104	1766 messages [RFC\\|4880, RFC\\|3156].
meillo@109	1767 Hence, the support for
meillo@104	1768 .Hd Encrypted
meillo@104	1769 header fields is removed in mmh.
meillo@109	1770 .Ci 064527f7b57ab050e5af13e15ad99aeeab125857
meillo@104	1771 .BU
meillo@84	1772 Native support for
meillo@84	1773 .Hd Face
meillo@104	1774 header fields has been removed, as well.
meillo@109	1775 .Ci 8e5be81f784682822f5e868c1bf3c8624682bd23
meillo@104	1776 This feature is similar to the
meillo@84	1777 .Hd X-Face
meillo@84	1778 header field in its intent,
meillo@21	1779 but takes a different approach to store the image.
meillo@84	1780 Instead of encoding the image data directly into the header field,
meillo@109	1781 it contains the hostname and UDP port where the image
meillo@109	1782 date can be retrieved.
meillo@109	1783 There exists even a third Face system,
meillo@109	1784 which is the successor of
meillo@109	1785 .Hd X-Face ,
meillo@109	1786 although it re-uses the
meillo@104	1787 .Hd Face
meillo@109	1788 header field.
meillo@109	1789 It was invented in 2005 and supports colored PNG images.
meillo@104	1790 None of the Face systems described here is popular today.
meillo@104	1791 Hence, mmh has no direct support for them.
meillo@104	1792 .BU
meillo@104	1793 The
meillo@104	1794 .Hd Content-MD5
meillo@104	1795 header field was introduced by RFC\\|1864.
meillo@104	1796 It provides detection of data corruption during the transfer.
meillo@104	1797 But it can not ensure verbatim end-to-end delivery of the contents
meillo@104	1798 [RFC\\|1864].
meillo@104	1799 The proper approach to verify content integrity in an
meillo@104	1800 end-to-end relationship is the use of digital cryptography.
meillo@104	1801 .\" XXX (RFCs FIXME).
meillo@104	1802 On the other hand, transfer protocols should detect corruption during
meillo@109	1803 the transmission.
meillo@109	1804 The TCP includes a checksum field therefore.
meillo@104	1805 These two approaches in combinations render the
meillo@104	1806 .Hd Content-MD5
meillo@104	1807 header field superfluous.
meillo@109	1808 Not a single one out of 4\\|200 messages from two decades
meillo@109	1809 in an nmh-workers mailing list archive contains a
meillo@104	1810 .Hd Content-MD5
meillo@104	1811 header field.
meillo@104	1812 Neither did any of the 60\\|000 messages in my personal mail storage.
meillo@104	1813 Removing the support for this header field,
meillo@104	1814 removed the last place where MD5 computation was needed.
meillo@109	1815 .Ci 31dc797eb5178970d68962ca8939da3fd9a8efda
meillo@104	1816 Hence, the MD5 code could be removed as well.
meillo@104	1817 Over 500 lines of code vanished by this one change.
meillo@104	1818
meillo@104	1819
meillo@104	1820 .U3 "MMDF maildrop support
meillo@21	1821 .P
meillo@104	1822 This type of format is conceptionally similar to the mbox format,
meillo@104	1823 but uses a different message delimiter (`\fL^A^A^A^A\fP' instead of
meillo@104	1824 `\fLFrom\0\fP').
meillo@104	1825 Mbox is the de-facto standard maildrop format on Unix,
meillo@109	1826 whereas the MMDF maildrop format became forgotten.
meillo@104	1827 I did drop MMDF maildrop format support.
meillo@109	1828 Mbox is the only packed mailbox format supported in mmh.
meillo@104	1829 .P
meillo@109	1830 The simplifications within the code were moderate.
meillo@109	1831 Mainly, the reading and writing of MMDF mailbox files was removed.
meillo@109	1832 But also, switches of
meillo@109	1833 .Pn packf
meillo@104	1834 and
meillo@109	1835 .Pn rcvpack
meillo@109	1836 could be removed.
meillo@109	1837 .Ci 3916ab66ad5d183705ac12357621ea8661afd3c0
meillo@109	1838 In the message parsing function
meillo@109	1839 .Fn sbr/m_getfld.c ,
meillo@109	1840 knowledge of MMDF packed mail boxes was removed.
meillo@109	1841 .Ci 684ec30d81e1223a282764452f4902ed4ad1c754
meillo@109	1842 Further code structure simplifications may be possible there,
meillo@109	1843 because only one single packed mailbox format is left to be supported.
meillo@104	1844 I have not worked on them yet because
meillo@104	1845 .Fu m_getfld()
meillo@104	1846 is heavily optimized and thus dangerous to touch.
meillo@104	1847 The risk of damaging the intricate workings of the optimized code is
meillo@104	1848 too high.
meillo@104	1849 .\" XXX: move somewhere else
meillo@104	1850 This problem is know to the developers of nmh, too.
meillo@109	1851 They also avoid touching this minefield.
meillo@104	1852
meillo@12	1853
meillo@101	1854 .U3 "Prompter's Control Keys
meillo@20	1855 .P
meillo@20	1856 The program
meillo@20	1857 .Pn prompter
meillo@104	1858 queries the user to fill in a message form.
meillo@104	1859 When used by
meillo@20	1860 .Pn comp
meillo@104	1861 as
meillo@104	1862 .Cl "comp -editor prompter" ,
meillo@20	1863 the resulting behavior is similar to
meillo@20	1864 .Pn mailx .
meillo@51	1865 Apparently,
meillo@20	1866 .Pn prompter
meillo@104	1867 hadn't been touched lately.
meillo@104	1868 Otherwise it's hardly explainable why it
meillo@20	1869 still offered the switches
meillo@84	1870 .Sw -erase
meillo@84	1871 .Ar chr
meillo@20	1872 and
meillo@84	1873 .Sw -kill
meillo@84	1874 .Ar chr
meillo@20	1875 to name the characters for command line editing.
meillo@21	1876 The times when this had been necessary are long time gone.
meillo@20	1877 Today these things work out-of-the-box, and if not, are configured
meillo@20	1878 with the standard tool
meillo@20	1879 .Pn stty .
meillo@104	1880 The switches are removed now
meillo@104	1881 .Ci 0bd9750710cdbab80cfb4036dd87af20afe1552f .
meillo@20	1882
meillo@104	1883
meillo@109	1884 .U3 "Hardcopy Terminal Support
meillo@21	1885 .P
meillo@109	1886 More of a funny anecdote is a check for being connected to a
meillo@109	1887 hardcopy terminal.
meillo@109	1888 It remained in the code until Spring 2012, when I finally removed it
meillo@104	1889 .Ci b7764c4a6b71d37918a97594d866258f154017ca .
meillo@109	1890 I would be truly happy to see such a terminal in action today,
meillo@109	1891 maybe even being able to work on it.
meillo@109	1892 But I fear my chances are null.
meillo@21	1893 .P
meillo@109	1894 The check only prevented a pager to be placed between the printing
meillo@104	1895 program (\c
meillo@104	1896 .Pn mhl )
meillo@104	1897 and the terminal.
meillo@109	1898 In nmh, this could have been ensured statically with the
meillo@104	1899 .Sw -nomoreproc
meillo@109	1900 at the command line, too.
meillo@109	1901 In mmh, seting the profile entry
meillo@104	1902 .Pe Pager
meillo@104	1903 or the environment variable
meillo@104	1904 .Ev PAGER
meillo@104	1905 to
meillo@109	1906 .Pn cat
meillo@109	1907 does the job.
meillo@104	1908
meillo@104	1909
meillo@21	1910
meillo@12	1911
meillo@58	1912 .H2 "Attachments
meillo@22	1913 .P
meillo@101	1914 The mind model of email attachments is unrelated to MIME.
meillo@101	1915 Although the MIME RFCs (2045 through 2049) define the technical
meillo@109	1916 requirements for having attachments, they do not mention the word
meillo@101	1917 ``attachment''.
meillo@101	1918 Instead of attachments, MIME talks about ``multi-part message bodies''
meillo@101	1919 [RFC\\|2045], a more general concept.
meillo@101	1920 Multi-part messages are messages
meillo@101	1921 ``in which one or more different
meillo@101	1922 sets of data are combined in a single body''
meillo@101	1923 [RFC\\|2046].
meillo@101	1924 MIME keeps its descriptions generic;
meillo@101	1925 it does not imply specific usage models.
meillo@109	1926 One usage model became prevalent: attachments.
meillo@101	1927 The idea is having a main text document with files of arbitrary kind
meillo@101	1928 attached to it.
meillo@101	1929 In MIME terms, this is a multi-part message having a text part first
meillo@110	1930 and parts of arbitrary type following.
meillo@101	1931 .P
meillo@101	1932 MH's MIME support is a direct implementation of the RFCs.
meillo@101	1933 The perception of the topic described in the RFCs is clearly visible
meillo@101	1934 in MH's implementation.
meillo@109	1935 In result, MH had all the MIME features but no idea of attachments.
meillo@109	1936 But users don't need all the MIME features,
meillo@109	1937 they want convenient attachment handling.
meillo@109	1938
meillo@102	1939
meillo@102	1940 .U3 "Composing MIME Messages
meillo@102	1941 .P
meillo@102	1942 In order to improve the situation on the message composing side,
meillo@102	1943 Jon Steinhart had added an attachment system to nmh in 2002.
meillo@101	1944 .Ci 7480dbc14bc90f2d872d434205c0784704213252
meillo@102	1945 In the file
meillo@102	1946 .Fn docs/README-ATTACHMENTS ,
meillo@102	1947 he described his motivation to do so as such:
meillo@101	1948 .QS
meillo@101	1949 Although nmh contains the necessary functionality for MIME message handing,
meillo@101	1950 the interface to this functionality is pretty obtuse.
meillo@101	1951 There's no way that I'm ever going to convince my partner to write
meillo@101	1952 .Pn mhbuild
meillo@101	1953 composition files!
meillo@101	1954 .QE
meillo@102	1955 .LP
meillo@102	1956 With this change, the mind model of attachments entered nmh.
meillo@102	1957 In the same document:
meillo@101	1958 .QS
meillo@101	1959 These changes simplify the task of managing attachments on draft files.
meillo@101	1960 They allow attachments to be added, listed, and deleted.
meillo@101	1961 MIME messages are automatically created when drafts with attachments
meillo@101	1962 are sent.
meillo@101	1963 .QE
meillo@102	1964 .LP
meillo@102	1965 Unfortunately, the attachment system,
meillo@102	1966 like any new facilities in nmh,
meillo@110	1967 was inactive by default.
meillo@101	1968 .P
meillo@101	1969 During my work in Argentina, I tried to improve the attachment system.
meillo@102	1970 But, because of great opposition in the nmh community,
meillo@102	1971 my patch died as a proposal on the mailing list, after long discussions.
meillo@101	1972 .[
meillo@101	1973 nmh-workers attachment proposal
meillo@101	1974 .]
meillo@110	1975 In January 2012, I extended the patch and applied it to mmh.
meillo@101	1976 .Ci 8ff284ff9167eff8f5349481529332d59ed913b1
meillo@102	1977 In mmh, the attachment system is active by default.
meillo@102	1978 Instead of command line switches, the
meillo@102	1979 .Pe Attachment-Header
meillo@102	1980 profile entry is used to specify
meillo@102	1981 the name of the attachment header field.
meillo@102	1982 It is pre-defined to
meillo@102	1983 .Hd Attach .
meillo@101	1984 .P
meillo@101	1985 To add an attachment to a draft, simply add an attachment header:
meillo@101	1986 .VS
meillo@101	1987 To: bob
meillo@101	1988 Subject: The file you wanted
meillo@101	1989 Attach: /path/to/the/file-bob-wanted
meillo@101	1990 --------
meillo@101	1991 Here it is.
meillo@101	1992 VE
meillo@101	1993 The header field can be added to the draft manually in the editor,
meillo@102	1994 or by using the `attach' command at the WhatNow prompt, or
meillo@102	1995 non-interactively with
meillo@101	1996 .Pn anno :
meillo@101	1997 .VS
meillo@102	1998 anno -append -nodate -component Attach -text /path/to/attachment
meillo@101	1999 VE
meillo@102	2000 Drafts with attachment headers are converted to MIME automatically by
meillo@102	2001 .Pn send .
meillo@102	2002 The conversion to MIME is invisible to the user.
meillo@102	2003 The draft stored in the draft folder is always in source form, with
meillo@101	2004 attachment headers.
meillo@101	2005 If the MIMEification fails, for instance because the file to attach
meillo@101	2006 is not accessible, the original draft is not changed.
meillo@101	2007 .P
meillo@102	2008 The attachment system handles the forwarding of messages, too.
meillo@101	2009 If the attachment header value starts with a plus character (`+'),
meillo@101	2010 like in
meillo@101	2011 .Cl "Attach: +bob 30 42" ,
meillo@101	2012 The given messages in the specified folder will be attached.
meillo@101	2013 This allowed to simplify
meillo@101	2014 .Pn forw .
meillo@101	2015 .Ci f41f04cf4ceca7355232cf7413e59afafccc9550
meillo@101	2016 .P
meillo@101	2017 Closely related to attachments is non-ASCII text content,
meillo@101	2018 because it requires MIME too.
meillo@102	2019 In nmh, the user needed to call `mime' at the WhatNow prompt
meillo@101	2020 to have the draft converted to MIME.
meillo@102	2021 This was necessary whenever the draft contained non-ASCII characters.
meillo@101	2022 If the user did not call `mime', a broken message would be sent.
meillo@101	2023 Therefore, the
meillo@101	2024 .Pe automimeproc
meillo@101	2025 profile entry could be specified to have the `mime' command invoked
meillo@102	2026 automatically each time.
meillo@101	2027 Unfortunately, this approach conflicted with with attachment system
meillo@101	2028 because the draft would already be in MIME format at the time
meillo@101	2029 when the attachment system wanted to MIMEify it.
meillo@102	2030 To use nmh's attachment system, `mime' must not be called at the
meillo@102	2031 WhatNow prompt and
meillo@101	2032 .Pe automimeproc
meillo@102	2033 must not be set in the profile.
meillo@101	2034 But then the case of non-ASCII text without attachment headers was
meillo@101	2035 not caught.
meillo@102	2036 All in all, the solution was complex and irritating.
meillo@102	2037 My patch from December 2010 would have simplified the situation.
meillo@102	2038 .P
meillo@101	2039 Mmh's current solution is even more elaborate.
meillo@101	2040 Any necessary MIMEification is done automatically.
meillo@101	2041 There is no `mime' command at the WhatNow prompt anymore.
meillo@102	2042 The draft will be converted automatically to MIME when either an
meillo@102	2043 attachment header or non-ASCII text is present.
meillo@101	2044 Further more, the special meaning of the hash character (`#')
meillo@102	2045 at line beginnings in the draft message is removed.
meillo@102	2046 Users need not at all deal with the whole topic.
meillo@101	2047 .P
meillo@102	2048 Although the new approach does not anymore support arbitrary MIME
meillo@102	2049 compositions directly, the full power of
meillo@101	2050 .Pn mhbuild
meillo@101	2051 can still be accessed.
meillo@102	2052 Given no attachment headers are included, the user can create
meillo@101	2053 .Pn mhbuild
meillo@102	2054 composition drafts like in nmh.
meillo@101	2055 Then, at the WhatNow prompt, he needs to invoke
meillo@101	2056 .Cl "edit mhbuild
meillo@101	2057 to convert it to MIME.
meillo@110	2058 Because the resulting draft does neither contain non-ASCII characters
meillo@102	2059 nor has it attachment headers, the attachment system will not touch it.
meillo@101	2060 .P
meillo@101	2061 The approach taken in mmh is taylored towards todays most common case:
meillo@101	2062 a text part with possibly attachments.
meillo@102	2063 This case is simplified a lot for users.
meillo@102	2064
meillo@102	2065 .U3 "MIME Type Guessing
meillo@102	2066 .P
meillo@102	2067 The use of
meillo@101	2068 .Pn mhbuild
meillo@102	2069 composition drafts had one notable advantage over attachment headers
meillo@102	2070 from the programmer's point of view: The user provides the appropriate
meillo@102	2071 MIME types for files to include.
meillo@102	2072 The attachment system needs to find out the correct MIME type itself.
meillo@102	2073 This is a difficult task, yet it spares the user irritating work.
meillo@102	2074 Determining the correct MIME type of content is partly mechanical,
meillo@102	2075 partly intelligent work.
meillo@102	2076 Forcing the user to find out the correct MIME type,
meillo@102	2077 forces him to do partly mechanical work.
meillo@102	2078 Letting the computer do the work, can lead to bad choices for difficult
meillo@102	2079 content.
meillo@102	2080 For mmh, the latter option was chosen.
meillo@102	2081 .P
meillo@102	2082 Determining the MIME type by the suffix of the file name is a dumb
meillo@102	2083 approach, yet it is simple to implement and provides good results
meillo@102	2084 for the common cases.
meillo@102	2085 Mmh implements this approach in the
meillo@102	2086 .Pn print-mimetype
meillo@102	2087 script.
meillo@102	2088 Using it is the default choice.
meillo@102	2089 .P
meillo@102	2090 A far better but less portable approach is the use of
meillo@102	2091 .Pn file .
meillo@102	2092 This standard tool tries to determine the type of files.
meillo@102	2093 Unfortunately, its capabilities and accuracy varies from system to system.
meillo@102	2094 Additionally, its output was only intended for human beings,
meillo@102	2095 but not to be used by programs.
meillo@102	2096 It varies much.
meillo@102	2097 Nevertheless, modern versions of GNU
meillo@102	2098 .Pn file ,
meillo@102	2099 which is prevalent on the popular GNU/Linux systems,
meillo@102	2100 provides MIME type output in machine-readable form.
meillo@102	2101 Although this solution is highly system-dependent,
meillo@102	2102 it solves the difficult problem well.
meillo@102	2103 On systems where GNU
meillo@102	2104 .Pn file ,
meillo@102	2105 version 5.04 or higher, is available it should be used.
meillo@102	2106 One needs to specify the following profile entry to do so:
meillo@102	2107 .VS
meillo@102	2108 Mime-Type-Query: file -b --mime
meillo@102	2109 VE
meillo@102	2110 .LP
meillo@102	2111 Other versions of
meillo@102	2112 .Pn file
meillo@102	2113 might possibly be usable with wrapper scripts to reformat the output.
meillo@102	2114 The diversity among
meillo@102	2115 .Pn file
meillo@102	2116 implementations is great; one needs to check the local variant.
meillo@102	2117 .P
meillo@102	2118 If no MIME type can be determined, text content gets sent as
meillo@102	2119 `text/plain' and anything else under the generic fall-back type
meillo@102	2120 `application/octet-stream'.
meillo@102	2121 It is not possible in mmh to override the automatic MIME type guessing
meillo@102	2122 for a specific file.
meillo@102	2123 To do so, the user would need to know in advance for which file
meillo@102	2124 the automatic guessing does fail, or the system would require interaction.
meillo@102	2125 I consider both cases impractical.
meillo@102	2126 The existing solution should be sufficient.
meillo@102	2127 If not, the user may always fall back to
meillo@102	2128 .Pn mhbuild
meillo@102	2129 composition drafts and ignore the attachment system.
meillo@101	2130
meillo@102	2131
meillo@102	2132 .U3 "Storing Attachments
meillo@102	2133 .P
meillo@108	2134 Extracting MIME parts of a message and storing them to disk is done by
meillo@108	2135 .Pn mhstore .
meillo@108	2136 The program has two operation modes,
meillo@108	2137 .Sw -auto
meillo@108	2138 and
meillo@108	2139 .Sw -noauto .
meillo@108	2140 With the former one, each part is stored under the filename given in the
meillo@108	2141 MIME part's meta information, if available.
meillo@108	2142 This naming information is usually available for modern attachments.
meillo@108	2143 If no filename is available, this MIME part is stored as if
meillo@108	2144 .Sw -noauto
meillo@108	2145 would have been specified.
meillo@108	2146 In the
meillo@108	2147 .Sw -noauto
meillo@108	2148 mode, the parts are processed according to rules, defined by
meillo@108	2149 .Pe mhstore-store-*
meillo@108	2150 profile entries.
meillo@108	2151 These rules define generic filename templates for storing
meillo@108	2152 or commands to post-process the contents in arbitrary ways.
meillo@108	2153 If no matching rule is available the part is stored under a generic
meillo@108	2154 filename, built from message number, MIME part number, and MIME type.
meillo@108	2155 .P
meillo@108	2156 The
meillo@108	2157 .Sw -noauto
meillo@108	2158 mode had been the default in nmh because it was considered safe,
meillo@108	2159 in contrast to the
meillo@108	2160 .Sw -auto
meillo@108	2161 mode.
meillo@108	2162 In mmh,
meillo@108	2163 .Sw -auto
meillo@108	2164 is not dangerous anymore.
meillo@108	2165 Two changes were necessary:
meillo@108	2166 .BU
meillo@108	2167 Any directory path is removed from the proposed filename.
meillo@108	2168 Thus, the files are always stored in the expected directory.
meillo@108	2169 .Ci 41b6eadbcecf63c9a66aa5e582011987494abefb
meillo@108	2170 .BU
meillo@108	2171 Tar files are not extracted automatically any more.
meillo@108	2172 Thus, the rest of the file system will not be touched.
meillo@108	2173 .Ci 94c80042eae3383c812d9552089953f9846b1bb6
meillo@108	2174 .LP
meillo@108	2175 Now, the outcome of mmh's
meillo@108	2176 .Cl "mhstore -auto
meillo@110	2177 can be foreseen from the output of
meillo@108	2178 .Cl "mhlist -verbose" .
meillo@108	2179 .P
meillo@108	2180 The
meillo@108	2181 .Sw -noauto
meillo@108	2182 mode is seen to be more powerful but less convenient.
meillo@108	2183 On the other hand,
meillo@108	2184 .Sw -auto
meillo@108	2185 is safe now and
meillo@108	2186 storing attachments under their original name is intuitive.
meillo@108	2187 Hence,
meillo@108	2188 .Sw -auto
meillo@108	2189 serves better as the default option.
meillo@108	2190 .Ci 3410b680416c49a7617491af38bc1929855a331d
meillo@108	2191 .P
meillo@108	2192 Files are stored into the directory given by the
meillo@108	2193 .Pe Nmh-Storage
meillo@108	2194 profile entry, if set, or
meillo@108	2195 into the current working directory, otherwise.
meillo@108	2196 Storing to different directories is only possible with
meillo@108	2197 .Pe mhstore-store-*
meillo@108	2198 profile entries.
meillo@108	2199 .P
meillo@108	2200 Still, in both modes, existing files get overwritten silently.
meillo@108	2201 This can be considered a bug.
meillo@108	2202 Yet, each other behavior has its draw-backs, too.
meillo@108	2203 Refusing to replace files requires adding a
meillo@108	2204 .Sw -force
meillo@108	2205 option.
meillo@108	2206 Users will likely need to invoke
meillo@108	2207 .Pn mhstore
meillo@108	2208 a second time with
meillo@108	2209 .Sw -force
meillo@108	2210 then.
meillo@108	2211 Eventually, only the user can decide in the concrete case.
meillo@108	2212 This requires interaction, which I like to avoid if possible.
meillo@108	2213 Appending a unique suffix to the filename is another bad option.
meillo@108	2214 For now, the behavior remains as it is.
meillo@108	2215 .P
meillo@108	2216 In mmh, only MIME parts of type message are special in
meillo@108	2217 .Pn mhstore 's
meillo@108	2218 .Sw -auto
meillo@108	2219 mode.
meillo@108	2220 Instead of storing message/rfc822 parts as files to disk,
meillo@108	2221 they are stored as messages into the current mail folder.
meillo@108	2222 The same applies to message/partial, only, the parts are reassembled
meillo@108	2223 automatically before.
meillo@108	2224 Parts of type message/external-body are not automatically retrieved
meillo@108	2225 anymore. Instead, Information on how to retrieve them is output.
meillo@108	2226 Not supporting this rare case saved nearly one thousand lines of code.
meillo@108	2227 .Ci 55e1d8c654ee0f7c45b9361ce34617983b454c32
meillo@108	2228 .\" XXX mention somewhere else too: (The profile entry `nmh-access-ftp'
meillo@108	2229 .\" and sbr/ruserpass.c for reading ~/.netrc are gone now.)
meillo@108	2230 Not special anymore is `application/octet-stream; type=tar'.
meillo@108	2231 Automatically extracting such MIME parts had been the dangerous part
meillo@108	2232 of the
meillo@108	2233 .Sw -auto
meillo@108	2234 mode.
meillo@108	2235 .Ci 94c80042eae3383c812d9552089953f9846b1bb6
meillo@108	2236
meillo@102	2237
meillo@102	2238
meillo@102	2239 .U3 "Showing MIME Messages
meillo@102	2240 .P
meillo@102	2241 FIXME
meillo@102	2242
meillo@58	2243
meillo@58	2244
meillo@58	2245 .H2 "Digital Cryptography
meillo@22	2246 .P
meillo@58	2247 Signing and encryption.
meillo@58	2248
meillo@58	2249
meillo@102	2250
meillo@102	2251 .H2 "Modern Defaults
meillo@22	2252 .P
meillo@102	2253 Just to give one example, for me it took one year of using nmh
meillo@102	2254 before I became aware of the existence of the attachment system.
meillo@102	2255 One could argue that this fact disqualifies my reading of the
meillo@102	2256 documentation.
meillo@102	2257 If I would have installed nmh from source back then, I could agree.
meillo@102	2258 Yet I had used a prepackaged version and had expected that it would
meillo@102	2259 just work.
meillo@58	2260
meillo@58	2261
meillo@58	2262
meillo@100	2263 .H1 "Code Style
meillo@22	2264 .P
meillo@58	2265 foo
meillo@58	2266
meillo@58	2267
meillo@58	2268 .H2 "Standard Code
meillo@22	2269 .P
meillo@58	2270 POSIX
meillo@22	2271
meillo@102	2272 .U3 "Converting to Standard Code
meillo@102	2273 .P
meillo@102	2274 One part of this task was converting obsolete code constructs
meillo@102	2275 to standard constructs.
meillo@102	2276 As I'm not even thirty years old and have no more than seven years of
meillo@102	2277 Unix experience, I needed to learn about the history in retrospective.
meillo@102	2278 Older people likely have used those ancient constructs themselves
meillo@102	2279 and have suffered from their incompatibilities and have longed for
meillo@102	2280 standardization.
meillo@102	2281 Unfortunately, I have only read that others had done so.
meillo@102	2282 This put me in a much more difficult positions when working on the old
meillo@102	2283 code.
meillo@102	2284 I needed to recherche what other would have known by heart from
meillo@102	2285 experience.
meillo@102	2286 All my programming experience comes from a time past ANSI C
meillo@102	2287 and past POSIX.
meillo@102	2288 Although I knew about the times before, I took the
meillo@102	2289 current state implicitly for granted most of the time.
meillo@102	2290 .P
meillo@102	2291 Being aware of
meillo@102	2292 these facts, I rather let people with more historic experience solve the
meillo@102	2293 task of converting the ancient code constructs to standardized ones.
meillo@102	2294 Luckily, Lyndon Nerenberg focused on this task at the nmh project.
meillo@102	2295 He converted large parts of the code to POSIX constructs, removing
meillo@102	2296 the conditionals compilation for now standardized features.
meillo@104	2297 I'm thankful for this task being solved.
meillo@104	2298 I only pulled the changes into
meillo@102	2299 mmh.
meillo@102	2300
meillo@102	2301
meillo@102	2302
meillo@22	2303
meillo@58	2304 .H2 "Separation
meillo@14	2305
meillo@58	2306 .U2 "MH Directory Split
meillo@0	2307 .P
meillo@19	2308 In MH and nmh, a personal setup had consisted of two parts:
meillo@19	2309 The MH profile, named
meillo@19	2310 .Fn \&.mh_profile
meillo@19	2311 and being located directly in the user's home directory.
meillo@19	2312 And the MH directory, where all his mail messages and also his personal
meillo@104	2313 forms, scan formats, other configuration files are stored.
meillo@104	2314 The location
meillo@104	2315 of this directory could be user-chosen.
meillo@104	2316 The default was to name it
meillo@19	2317 .Fn Mail
meillo@19	2318 and have it directly in the home directory.
meillo@19	2319 .P
meillo@19	2320 I've never liked the data storage and the configuration to be intermixed.
meillo@104	2321 They are different kinds of data.
meillo@104	2322 One part, are the messages,
meillo@104	2323 which are the data to operate on.
meillo@104	2324 The other part, are the personal
meillo@19	2325 configuration files, which are able to change the behavior of the operations.
meillo@19	2326 The actual operations are defined in the profile, however.
meillo@19	2327 .P
meillo@19	2328 When storing data, one should try to group data by its type.
meillo@19	2329 There's sense in the Unix file system hierarchy, where configuration
meillo@19	2330 file are stored separate (\c
meillo@19	2331 .Fn /etc )
meillo@19	2332 to the programs (\c
meillo@19	2333 .Fn /bin
meillo@19	2334 and
meillo@19	2335 .Fn /usr/bin )
meillo@19	2336 to their sources (\c
meillo@19	2337 .Fn /usr/src ).
meillo@19	2338 Such separation eases the backup management, for instance.
meillo@19	2339 .P
meillo@19	2340 In mmh, I've reorganized the file locations.
meillo@19	2341 Still there are two places:
meillo@19	2342 There's the mail storage directory, which, like in MH, contains all the
meillo@19	2343 messages, but, unlike in MH, nothing else.
meillo@19	2344 Its location still is user-chosen, with the default name
meillo@19	2345 .Fn Mail ,
meillo@104	2346 in the user's home directory.
meillo@104	2347 This is much similar to the case in nmh.
meillo@19	2348 The configuration files, however, are grouped together in the new directory
meillo@19	2349 .Fn \&.mmh
meillo@19	2350 in the user's home directory.
meillo@19	2351 The user's profile now is a file, named
meillo@19	2352 .Fn profile ,
meillo@19	2353 in this mmh directory.
meillo@19	2354 Consistently, the context file and all the personal forms, scan formats,
meillo@19	2355 and the like, are also there.
meillo@19	2356 .P
meillo@19	2357 The naming changed with the relocation.
meillo@19	2358 The directory where everything, except the profile, had been stored (\c
meillo@19	2359 .Fn $HOME/Mail ),
meillo@104	2360 used to be called \fIMH directory\fP.
meillo@104	2361 Now, this directory is called the
meillo@104	2362 user's \fImail storage\fP.
meillo@104	2363 The name \fImmh directory\fP is now given to
meillo@19	2364 the new directory
meillo@19	2365 (\c
meillo@19	2366 .Fn $HOME/.mmh ),
meillo@19	2367 containing all the personal configuration files.
meillo@19	2368 .P
meillo@19	2369 The separation of the files by type of content is logical and convenient.
meillo@19	2370 There are no functional differences as any possible setup known to me
meillo@19	2371 can be implemented with both approaches, although likely a bit easier
meillo@104	2372 with the new approach.
meillo@104	2373 The main goal of the change had been to provide
meillo@19	2374 sensible storage locations for any type of personal mmh file.
meillo@19	2375 .P
meillo@19	2376 In order for one user to have multiple MH setups, he can use the
meillo@19	2377 environment variable
meillo@19	2378 .Ev MH
meillo@19	2379 the point to a different profile file.
meillo@19	2380 The MH directory (mail storage plus personal configuration files) is
meillo@19	2381 defined by the
meillo@19	2382 .Pe Path
meillo@19	2383 profile entry.
meillo@19	2384 The context file could be defined by the
meillo@19	2385 .Pe context
meillo@19	2386 profile entry or by the
meillo@19	2387 .Ev MHCONTEXT
meillo@19	2388 environment variable.
meillo@19	2389 The latter is useful to have a distinct context (e.g. current folders)
meillo@19	2390 in each terminal window, for instance.
meillo@19	2391 In mmh, there are three environment variables now.
meillo@19	2392 .Ev MMH
meillo@19	2393 may be used to change the location of the mmh directory.
meillo@19	2394 .Ev MMHP
meillo@19	2395 and
meillo@19	2396 .Ev MMHC
meillo@19	2397 change the profile and context files, respectively.
meillo@19	2398 Besides providing a more consistent feel (which simply is the result
meillo@19	2399 of being designed anew), the set of personal configuration files can
meillo@19	2400 be chosen independently from the profile (including mail storage location)
meillo@104	2401 and context, now.
meillo@104	2402 Being it relevant for practical use or not, it
meillo@104	2403 de-facto is an improvement.
meillo@104	2404 However, the main achievement is the
meillo@19	2405 split between mail storage and personal configuration files.
meillo@17	2406
meillo@0	2407
meillo@58	2408 .H2 "Modularization
meillo@0	2409 .P
meillo@58	2410 whatnowproc
meillo@0	2411 .P
meillo@49	2412 The \fIMH library\fP
meillo@49	2413 .Fn libmh.a
meillo@49	2414 collects a bunch of standard functions that many of the MH tools need,
meillo@49	2415 like reading the profile or context files.
meillo@49	2416 This doesn't hurt the separation.
meillo@49	2417
meillo@58	2418
meillo@58	2419 .H2 "Style
meillo@58	2420 .P
meillo@58	2421 Code layout, goto, ...
meillo@58	2422
meillo@102	2423 .P
meillo@102	2424 anno rework
meillo@102	2425
meillo@58	2426
meillo@58	2427
meillo@58	2428
meillo@89	2429 .H1 "Concept Exploitation/Homogeneity
meillo@58	2430
meillo@58	2431
meillo@58	2432 .H2 "Draft Folder
meillo@58	2433 .P
meillo@58	2434 Historically, MH provided exactly one draft message, named
meillo@58	2435 .Fn draft
meillo@58	2436 and
meillo@104	2437 being located in the MH directory.
meillo@104	2438 When starting to compose another message
meillo@58	2439 before the former one was sent, the user had been questioned whether to use,
meillo@104	2440 refile or replace the old draft.
meillo@104	2441 Working on multiple drafts at the same time
meillo@104	2442 was impossible.
meillo@104	2443 One could only work on them in alteration by refiling the
meillo@104	2444 previous one to some directory and fetching some other one for reediting.
meillo@58	2445 This manual draft management needed to be done each time the user wanted
meillo@58	2446 to switch between editing one draft to editing another.
meillo@58	2447 .P
meillo@58	2448 To allow true parallel editing of drafts, in a straight forward way, the
meillo@104	2449 draft folder facility exists.
meillo@104	2450 It had been introduced already in July 1984
meillo@104	2451 by Marshall T. Rose.
meillo@110	2452 The facility was inactive by default.
meillo@110	2453 Even in nmh, the draft folder facility remained inactive by default.
meillo@58	2454 At least, Richard Coleman added the man page
meillo@58	2455 .Mp mh-draft(5)
meillo@58	2456 to document
meillo@58	2457 the feature well.
meillo@58	2458 .P
meillo@58	2459 The only advantage of not using the draft folder facility is the static
meillo@104	2460 name of the draft file.
meillo@104	2461 This could be an issue for MH front-ends like mh-e.
meillo@58	2462 But as they likely want to provide working on multiple drafts in parallel,
meillo@104	2463 the issue is only concerning compatibility.
meillo@104	2464 The aim of nmh to stay compatible
meillo@58	2465 prevented the default activation of the draft folder facility.
meillo@58	2466 .P
meillo@58	2467 On the other hand, a draft folder is the much more natural concept than
meillo@104	2468 a draft message.
meillo@104	2469 MH's mail storage consists of folders and messages,
meillo@104	2470 the messages named with ascending numbers.
meillo@104	2471 A draft message breaks with this
meillo@58	2472 concept by introducing a message in a file named
meillo@58	2473 .Fn draft .
meillo@58	2474 This draft
meillo@104	2475 message is special.
meillo@104	2476 It can not be simply listed with the available tools,
meillo@104	2477 but instead requires special switches.
meillo@104	2478 I.e. corner-cases were
meillo@104	2479 introduced.
meillo@104	2480 A draft folder, in contrast, does not introduce such
meillo@104	2481 corner-cases.
meillo@104	2482 The available tools can operate on the messages within that
meillo@104	2483 folder like on any messages within any mail folders.
meillo@104	2484 The only difference
meillo@58	2485 is the fact that the default folder for
meillo@58	2486 .Pn send
meillo@58	2487 is the draft folder,
meillo@58	2488 instead of the current folder, like for all other tools.
meillo@58	2489 .P
meillo@58	2490 The trivial part of the change was activating the draft folder facility
meillo@104	2491 by default and setting a default name for this folder.
meillo@104	2492 Obviously, I chose
meillo@58	2493 the name
meillo@58	2494 .Fn +drafts .
meillo@58	2495 This made the
meillo@82	2496 .Sw -draftfolder
meillo@58	2497 and
meillo@82	2498 .Sw -draftmessage
meillo@58	2499 switches useless, and I could remove them.
meillo@58	2500 The more difficult but also the part that showed the real improvement,
meillo@58	2501 was updating the tools to the new concept.
meillo@82	2502 .Sw -draft
meillo@58	2503 switches could
meillo@58	2504 be dropped, as operating on a draft message became indistinguishable to
meillo@58	2505 operating on any other message for the tools.
meillo@58	2506 .Pn comp
meillo@58	2507 still has its
meillo@82	2508 .Sw -use
meillo@58	2509 switch for switching between its two modes: (1) Compose a new
meillo@104	2510 draft, possibly by taking some existing message as a form.
meillo@104	2511 (2) Modify
meillo@104	2512 an existing draft.
meillo@104	2513 In either case, the behavior of
meillo@58	2514 .Pn comp is
meillo@104	2515 deterministic.
meillo@104	2516 There is no more need to query the user.
meillo@104	2517 I consider this
meillo@104	2518 a major improvement.
meillo@104	2519 By making
meillo@58	2520 .Pn send
meillo@58	2521 simply operate on the current
meillo@58	2522 message in the draft folder by default, with message and folder both
meillo@58	2523 overridable by specifying them on the command line, it is now possible
meillo@58	2524 to send a draft anywhere within the storage by simply specifying its folder
meillo@58	2525 and name.
meillo@58	2526 .P
meillo@58	2527 All theses changes converted special cases to regular cases, thus
meillo@58	2528 simplifying the tools and increasing the flexibility.
meillo@58	2529
meillo@58	2530
meillo@58	2531 .H2 "Trash Folder
meillo@58	2532 .P
meillo@58	2533 Similar to the situation for drafts is the situation for removed messages.
meillo@104	2534 Historically, a message was deleted by renaming.
meillo@104	2535 A specific
meillo@58	2536 \fIbackup prefix\fP, often comma (\c
meillo@58	2537 .Fn , )
meillo@58	2538 or hash (\c
meillo@58	2539 .Fn # ),
meillo@104	2540 being prepended to the file name.
meillo@104	2541 Thus, MH wouldn't recognize the file
meillo@58	2542 as a message anymore, as only files whose name consists of digits only
meillo@104	2543 are treated as messages.
meillo@104	2544 The removed messages remained as files in the
meillo@58	2545 same directory and needed some maintenance job to truly delete them after
meillo@104	2546 some grace time.
meillo@104	2547 Usually, by running a command similar to
meillo@82	2548 .VS
meillo@82	2549 find /home/user/Mail -ctime +7 -name ',*' \| xargs rm
meillo@82	2550 VE
meillo@104	2551 in a cron job.
meillo@104	2552 Within the grace time interval
meillo@58	2553 the original message could be restored by stripping the
meillo@104	2554 the backup prefix from the file name.
meillo@104	2555 If however, the last message of
meillo@58	2556 a folder is been removed \(en say message
meillo@58	2557 .Fn 6
meillo@58	2558 becomes file
meillo@58	2559 .Fn ,6
meillo@58	2560 \(en and a new message enters the same folder, thus the same
meillo@58	2561 numbered being given again \(en in our case
meillo@58	2562 .Fn 6
meillo@58	2563 \(en, if that one
meillo@58	2564 is removed too, then the backup of the former message gets overwritten.
meillo@58	2565 Thus, the ability to restore removed messages does not only depend on
meillo@58	2566 the ``sweeping cron job'' but also on the removing of further messages.
meillo@58	2567 This is undesirable, because the real mechanism is hidden from the user
meillo@58	2568 and the consequences of further removals are not always obvious.
meillo@58	2569 Further more, the backup files are scattered within the whole mail
meillo@58	2570 storage, instead of being collected at one place.
meillo@58	2571 .P
meillo@58	2572 To improve the situation, the profile entry
meillo@58	2573 .Pe rmmproc
meillo@58	2574 (previously named
meillo@58	2575 .Pe Delete-Prog )
meillo@58	2576 was introduced, very early.
meillo@58	2577 It could be set to any command, which would care for the mail removal
meillo@58	2578 instead of taking the default action, described above.
meillo@58	2579 Refiling the to-be-removed files to some garbage folder was a common
meillo@104	2580 example.
meillo@104	2581 Nmh's man page
meillo@58	2582 .Mp rmm(1)
meillo@58	2583 proposes
meillo@58	2584 .Cl "refile +d
meillo@58	2585 to move messages to the garbage folder and
meillo@58	2586 .Cl "rm `mhpath +d all`
meillo@58	2587 the empty the garbage folder.
meillo@104	2588 Managing the message removal this way is a sane approach.
meillo@104	2589 It keeps
meillo@58	2590 the removed messages in one place, makes it easy to remove the backup
meillo@58	2591 files, and, most important, enables the user to use the tools of MH
meillo@104	2592 itself to operate on the removed messages.
meillo@104	2593 One can
meillo@58	2594 .Pn scan
meillo@58	2595 them,
meillo@58	2596 .Pn show
meillo@58	2597 them, and restore them with
meillo@58	2598 .Pn refile .
meillo@58	2599 There's no more
meillo@58	2600 need to use
meillo@58	2601 .Pn mhpath
meillo@58	2602 to switch over from MH tools to Unix tools \(en MH can do it all itself.
meillo@58	2603 .P
meillo@58	2604 This approach matches perfect with the concepts of MH, thus making
meillo@104	2605 it powerful.
meillo@104	2606 Hence, I made it the default.
meillo@104	2607 And even more, I also
meillo@58	2608 removed the old backup prefix approach, as it is clearly less powerful.
meillo@58	2609 Keeping unused alternative in the code is a bad choice as they likely
meillo@104	2610 gather bugs, by not being constantly tested.
meillo@104	2611 Also, the increased code
meillo@104	2612 size and more conditions crease the maintenance costs.
meillo@104	2613 By strictly
meillo@58	2614 converting to the trash folder approach, I simplified the code base.
meillo@58	2615 .Pn rmm
meillo@58	2616 calls
meillo@58	2617 .Pn refile
meillo@58	2618 internally to move the to-be-removed
meillo@58	2619 message to the trash folder (\c
meillo@58	2620 .Fn +trash
meillo@104	2621 by default).
meillo@104	2622 Messages
meillo@58	2623 there can be operated on like on any other message in the storage.
meillo@58	2624 The sweep clean, one can use
meillo@82	2625 .Cl "rmm -unlink +trash a" ,
meillo@58	2626 where the
meillo@82	2627 .Sw -unlink
meillo@58	2628 switch causes the files to be truly unliked instead
meillo@58	2629 of moved to the trash folder.
meillo@58	2630
meillo@58	2631
meillo@58	2632 .H2 "Path Notations
meillo@58	2633 .P
meillo@58	2634 foo
meillo@58	2635
meillo@58	2636
meillo@58	2637 .H2 "MIME Integration
meillo@58	2638 .P
meillo@58	2639 user-visible access to whole messages and MIME parts are inherently
meillo@58	2640 different
meillo@58	2641
meillo@58	2642
meillo@58	2643 .H2 "Of One Cast
meillo@58	2644 .P