meillo@58: .H0 "Discussion
meillo@0: .P
meillo@58: This main chapter discusses the practical work done in the mmh project.
meillo@58: It is structured along the goals to achieve. The concrete work done
meillo@58: is described in the examples of how the general goals were achieved.
meillo@87: The discussion compares the current version of mmh with the state of
meillo@87: nmh just before the mmh project started, i.e. Fall 2011.
meillo@87: Current changes of nmh will be mentioned only as side notes.
meillo@87: .\" XXX where do I discuss the parallel development of nmh?
meillo@58: 
meillo@58: 
meillo@58: 
meillo@58: .H1 "Stream-lining
meillo@58: 
meillo@0: .P
meillo@58: MH had been considered an all-in-one system for mail handling.
meillo@58: The community around nmh has a similar understanding.
meillo@87: In fundamental difference, mmh shall be a MUA only.
meillo@87: I believe that the development of all-in-one mail systems is obsolete.
meillo@87: Today, email is too complex to be fully covered by single projects.
meillo@87: Such a project won't be able to excel in all aspects.
meillo@87: Instead, the aspects of email should be covered my multiple projects,
meillo@87: which then can be combined to form a complete system.
meillo@87: Excellent implementations for the various aspects of email exist already.
meillo@87: Just to name three examples: Postfix is a specialized MTA,
meillo@87: Procmail is a specialized MDA, and Fetchmail is a specialized MRA.
meillo@87: I believe that it is best to use such specilized tools instead of
meillo@87: providing the same function again as a side-component in the project.
meillo@58: .P
meillo@87: Doing something well, requires to focus on a small set of specific aspects.
meillo@87: Under the assumption that focused development produces better results
meillo@87: in the particular area, specialized projects will likely be superior
meillo@87: in their field of focus.
meillo@87: Hence, all-in-one mail system projects \(en no matter if monolithic
meillo@87: or modular \(en will never be the best choice in any of the fields.
meillo@87: Even in providing the best consistent all-in-one system they are likely
meillo@87: to be beaten by projects that focus only on integrating existing mail
meillo@87: components to a homogenious system.
meillo@87: .P
meillo@87: The limiting resource in Free Software community development
meillo@87: is usually man power.
meillo@87: If the development power is spread over a large development area,
meillo@87: it becomes even more difficult to compete with the specialists in the
meillo@87: various fields.
meillo@87: The concrete situation for MH-based mail systems is even tougher,
meillo@87: given the small and aged community, including both developers and users,
meillo@87: it has.
meillo@87: .P
meillo@87: In consequence, I believe that the available development resources
meillo@87: should be focused on the point where MH is most unique.
meillo@87: This is clearly the user interface \(en the MUA.
meillo@87: Peripheral parts should be removed to stream-line mmh for the MUA task.
meillo@60: 
meillo@60: 
meillo@87: .H2 "Removal of the Mail Transfer Facilities
meillo@60: .P
meillo@60: In contrast to nmh, which also provides mail submission and mail retrieval
meillo@87: agents, mmh is a MUA only.
meillo@66: This general difference in the view on the character of nmh
meillo@76: initiated the development of mmh.
meillo@66: Removing the mail transfer facilities had been the first work task
meillo@76: in the mmh project.
meillo@60: .P
meillo@66: The MSA is called \fIMessage Transfer Service\fP (MTS) in nmh.
meillo@76: The facility established network connections and spoke SMTP to submit
meillo@60: messages for relay to the outside world.
meillo@76: This part was implemented by the
meillo@60: .Pn post
meillo@60: command.
meillo@87: The changes in emailing in the last years
meillo@87: demanded changes in this part of nmh too.
meillo@76: Encryption and authetication for network connections
meillo@87: needed to be supported, hence TLS and SASL were introduced into nmh.
meillo@87: This added complexity to nmh without improving it in its core functions.
meillo@87: Also, keeping up with recent developments in the field of
meillo@87: mail transfer requires development power and specialists.
meillo@87: In mmh this whole facility was simply cut off.
meillo@76: .Ci f6aa95b724fd8c791164abe7ee5468bf5c34f226
meillo@76: .Ci fecd5d34f65597a4dfa16aeabea7d74b191532c3
meillo@76: .Ci 156d35f6425bea4c1ed3c4c79783dc613379c65b
meillo@87: Instead, mmh depends on an external MSA.
meillo@60: The only outgoing interface available to mmh is the
meillo@60: .Pn sendmail
meillo@87: command, which almost any MSA provides.
meillo@87: If not, a wrapper program can be written.
meillo@87: It must read the message from the standard input, extract the
meillo@87: recipient addresses from the message header, and hand the message
meillo@87: over to the MSA.
meillo@87: For example, a wrapper script for qmail would be:
meillo@87: .VS
meillo@87: #!/bin/sh
meillo@87: # ignore command line arguments
meillo@87: exec qmail-inject
meillo@87: VE
meillo@87: The requirement to parse the recipient addresses out of the message header 
meillo@87: is likely to be removed in the future.
meillo@87: Then mmh would give the recipient addresses as command line arguments.
meillo@87: This is clearly the better interface, but mmh does not provide it yet.
meillo@87: .\" XXX implement it
meillo@60: .P
meillo@60: To retrieve mail, the
meillo@60: .Pn inc
meillo@76: command established network connections
meillo@76: and spoke POP3 to retrieve mail from remote servers.
meillo@76: As with mail submission, the network connections required encryption and
meillo@87: authentication, thus TLS and SASL were added.
meillo@87: Support for message retrieval through IMAP will become necessary
meillo@87: to be added soon, too, and so on for any changes in mail transfer.
meillo@76: Mmh has dropped the support for retrieving mail from remote locations.
meillo@76: .Ci ab7b48411962d26439f92f35ed084d3d6275459c
meillo@76: Instead, it depends on an external tool to cover this task.
meillo@87: In mmh there exist two paths for messages to enter mmh's mail storage:
meillo@87: (1) Mail can be incorporate with
meillo@60: .Pn inc
meillo@87: from the system maildrop, or (2) with
meillo@60: .Pn rcvstore
meillo@87: by reading them, one at a time, from the standard input.
meillo@60: .P
meillo@60: With the removal of the MSA and MRA, mmh converted from an all-in-one
meillo@87: mail system to being a MUA only.
meillo@87: Following the Unix philosophy, it now focuses on one job and
meillo@76: tries to do that one well.
meillo@76: Not only the programs follow that tenet but also the project itself does so.
meillo@60: Now, of course, mmh depends on third-party software.
meillo@87: An external MSA is required to transfer mail to the outside world;
meillo@60: an external MRA is required to retrieve mail from remote machines.
meillo@60: There exist excellent implementations of such software,
meillo@76: which do this specific task likely better than the internal
meillo@87: versions had done it.
meillo@87: Also, the best suiting programs can be freely chosen.
meillo@60: .P
meillo@60: As it had already been possible to use an external MSA or MRA,
meillo@60: why not keep the internal version for convenience?
meillo@76: The question whether there is sense in having a fall-back pager in all
meillo@76: the command line tools, for the cases when
meillo@60: .Pn more
meillo@60: or
meillo@60: .Pn less
meillo@76: aren't available, appears to be ridiculous.
meillo@87: Now, an MSA or MRA is more complex than a text pager
meillo@87: and not necessarily available but still the concept of orthogonal
meillo@87: design holds: ``Write programs that do one thing and do it well.''
meillo@87: .[
meillo@87: mcilroy unix phil
meillo@87: p. 53
meillo@87: .]
meillo@87: .[
meillo@87: mcilroy bstj foreword
meillo@87: .]
meillo@87: Here, this part of the Unix philosophy was applied not only
meillo@87: to the programs but to the project itself.
meillo@87: In other words:
meillo@87: ``Develop projects that focus on one thing and do it well.''
meillo@87: Projects grown complex should be split for the same reasons programs grown
meillo@87: complex should be split.
meillo@87: If it is conceptionally more elegant to have the MSA and MRA
meillo@87: separate projects then they should be separated.
meillo@87: This is the case here, in my opinion.
meillo@87: The RFCs propose this separation by clearly distinguishing the different
meillo@87: mail handling tasks.
meillo@87: .[
meillo@87: rfc 821
meillo@87: .]
meillo@87: The small interfaces between the mail agents support the separation.
meillo@76: .P
meillo@87: In the beginning, email had been small and simple.
meillo@76: (\c
meillo@60: .Pn /bin/mail
meillo@76: had once covered anything there was to email and still had been small
meillo@76: and simple.)
meillo@76: Then the essential complexity of email increased.
meillo@87: (Essential complexity is the complexity defined by the problem itself.\0
meillo@87: .[[
meillo@87: brooks no silver bullet
meillo@87: .]])
meillo@87: Email systems reacted to this change: They grew.
meillo@87: RFCs started to introduce mail agents and separated the various tasks
meillo@87: because the existing tasks became more extensive and new tasks appeared.
meillo@87: Again, email systems grew, or they split parts off.
meillo@76: In nmh, for instance, the POP server, which the original MH had included,
meillo@76: was removed.
meillo@87: Now is the time to go one step further and remove the MSA and MRA, too.
meillo@87: Not only does this decrease the code size of the project,
meillo@87: but, more important, it unburdens mmh of the whole field of
meillo@87: message transfer with all its implications for the project.
meillo@87: There's no more need to concern with changes in network transfer.
meillo@76: This independence is received by depending on an external program
meillo@76: that covers the field.
meillo@76: Today, this is a reasonable exchange.
meillo@60: .P
meillo@87: Function can be added in three different ways:
meillo@87: .BU
meillo@87: Implementing the function originally in the project.
meillo@87: .BU
meillo@87: Depending on a library that provides the function.
meillo@87: .BU
meillo@87: Depending on a program that provides the function.
meillo@87: .P
meillo@87: Whereas adding the function originally to the project increases the
meillo@76: code size most and requires most maintenance and development work,
meillo@87: it makes the project most independent of other software.
meillo@87: Using libraries or external programs require less maintenance work
meillo@87: but introduces dependencies on external software.
meillo@87: Programs have the smallest interfaces and provide the best separation
meillo@87: but possibly limit the information exchange.
meillo@87: External libraries are stronger connected than external programs,
meillo@87: thus information can be exchanged more flexible.
meillo@87: Adding code to a project increases maintenance work.
meillo@87: .\" XXX ref
meillo@87: Implementing complex functions originally in the project will add
meillo@87: a lot of code.
meillo@87: This should be avoided if possible.
meillo@66: Hence, the dependencies only change in kind, not in their existence.
meillo@66: In mmh, library dependencies on
meillo@66: .Pn libsasl2
meillo@66: and
meillo@66: .Pn libcrypto /\c
meillo@66: .Pn libssl
meillo@66: were treated against program dependencies on an MSA and an MRA.
meillo@87: This also meant treating build-time dependencies against run-time
meillo@87: dependencies.
meillo@66: Besides program dependencies providing the stronger separation
meillo@66: and being more flexible, they also allowed
meillo@66: over 6\|000 lines of code to be removed from mmh.
meillo@66: This made mmh's code base about 12\|% smaller.
meillo@87: Reducing the project's code size by such an amount without actually
meillo@87: losing functionality is a convincing argument.
meillo@87: Actually, as external MSAs and MRAs are likely superior to the
meillo@87: project's internal versions, the common user even gains functionality.
meillo@66: .P
meillo@76: Users of MH should not have problems to set up an external MSA and MRA.
meillo@60: Also, the popular MSAs and MRAs have large communities and a lot
meillo@60: of documentation available.
meillo@87: Choices for MSAs range from full-featured MTAs like
meillo@60: .I Postfix
meillo@87: over mid-size MTAs like
meillo@60: .I masqmail
meillo@60: and
meillo@60: .I dma
meillo@60: to small forwarders like
meillo@60: .I ssmtp
meillo@60: and
meillo@60: .I nullmailer .
meillo@60: Choices for MRAs include
meillo@60: .I fetchmail ,
meillo@60: .I getmail ,
meillo@60: .I mpop
meillo@60: and
meillo@60: .I fdm .
meillo@60: 
meillo@60: 
meillo@60: .H2 "Removal of non-MUA Tools
meillo@60: .P
meillo@87: One goal of mmh is to remove the tools that are not part of the MUA's task.
meillo@87: Further more, any tools that don't improve the MUA's job significently
meillo@87: should be removed.
meillo@87: Loosely related and rarely used tools distract from the lean appearance.
meillo@87: They require maintenance work without adding much to the core task.
meillo@87: On removing these tools, the project shall become more stream-lined
meillo@87: and focused.
meillo@76: In mmh the following tools are not available anymore:
meillo@62: .BU
meillo@58: .Pn conflict
meillo@87: was removed
meillo@76: .Ci 8b235097cbd11d728c07b966cf131aa7133ce5a9
meillo@87: because it is a mail system maintenance tool that is not MUA-related.
meillo@87: It even checked
meillo@58: .Fn /etc/passwd
meillo@58: and
meillo@58: .Fn /etc/group
meillo@87: for consistency, which is completely unrelated to email.
meillo@87: A tool like
meillo@87: .Pn conflict
meillo@87: is surely useful, but it should not be shipped with mmh.
meillo@76: .\" XXX historic reasons?
meillo@62: .BU
meillo@58: .Pn rcvtty
meillo@87: was removed
meillo@87: .Ci 14767c94b3827be7c867196467ed7aea5f6f49b0
meillo@87: because its usecase of writing to the user's terminal
meillo@76: on receiving of mail is obsolete.
meillo@87: If users like to be informed of new mail, the shell's
meillo@58: .Ev MAILPATH
meillo@87: variable or graphical notifications are technically more appealing.
meillo@62: Writing directly to a terminals is hardly ever wanted today.
meillo@62: If though one wants to have it this way, the standard tool
meillo@58: .Pn write
meillo@58: can be used in a way similar to:
meillo@82: .VS
meillo@58: scan -file - | write `id -un`
meillo@82: VE
meillo@62: .BU
meillo@58: .Pn viamail
meillo@87: was removed
meillo@87: .Ci eda72d6a7a7c20ff123043fb7f19c509ea01f932
meillo@87: when the new attachment system was activated, because
meillo@58: .Pn forw
meillo@76: could then cover the task itself.
meillo@62: The program
meillo@58: .Pn sendfiles
meillo@62: was rewritten as a shell script wrapper around
meillo@58: .Pn forw .
meillo@76: .Ci 0e82199cf3c991a173e0ac8aa776efdb3ded61e6
meillo@62: .BU
meillo@58: .Pn msgchk
meillo@87: was removed
meillo@87: .Ci bb9360ead7eb7a3fedcce2eeedfc660014e41dbe ,
meillo@87: because it lost its use case when POP support was removed.
meillo@76: A call to
meillo@58: .Pn msgchk
meillo@87: provided hardly more information than:
meillo@82: .VS
meillo@58: ls -l /var/mail/meillo
meillo@82: VE
meillo@87: It did distinguished between old and new mail, but
meillo@87: this detail information and can be retrieved with
meillo@76: .Pn stat (1),
meillo@62: too.
meillo@62: A very small shell script could be written to output the information
meillo@76: in a similar way, if truly necessary.
meillo@76: As mmh's
meillo@76: .Pn inc
meillo@87: only incorporates mail from the user's local maildrop,
meillo@62: and thus no data transfers over slow networks are involved,
meillo@76: there's hardly any need to check for new mail before incorporating it.
meillo@62: .BU
meillo@58: .Pn msh
meillo@87: was removed
meillo@76: .Ci 916690191222433a6923a4be54b0d8f6ac01bd02
meillo@87: because the tool was in conflict with the philosophy of MH.
meillo@76: It provided an interactive shell to access the features of MH,
meillo@76: but it wasn't just a shell, tailored to the needs of mail handling.
meillo@76: Instead it was one large program that had several MH tools built in.
meillo@76: This conflicts with the major feature of MH of being a tool chest.
meillo@76: .Pn msh 's
meillo@76: main use case had been accessing Bulletin Boards, which have seized to
meillo@62: be popular.
meillo@62: .P
meillo@62: Removing
meillo@58: .Pn msh ,
meillo@76: together with the truly archaic code relicts
meillo@58: .Pn vmh
meillo@58: and
meillo@58: .Pn wmh ,
meillo@62: saved more than 7\|000 lines of C code \(en
meillo@66: about 15\|% of the project's original source code amount.
meillo@76: .P
meillo@76: Having less code (with equal readability, of course)
meillo@76: for the same functionality is an advantage.
meillo@63: Less code means less bugs and less maintenance work.
meillo@76: As
meillo@63: .Pn rcvtty
meillo@63: and
meillo@63: .Pn msgchk
meillo@87: are assumed to be rarely used and can be implemented in different ways,
meillo@87: why should one keep them?
meillo@76: Removing them stream-lines mmh.
meillo@63: .Pn viamail 's
meillo@63: use case is now partly obsolete and partly covered by
meillo@63: .Pn forw ,
meillo@76: hence there's no reason to still maintain it.
meillo@63: .Pn conflict
meillo@76: is not related to the mail client, and
meillo@63: .Pn msh
meillo@63: conflicts with the basic concept of MH.
meillo@76: Theses two tools might still be useful, but they should not be part of mmh.
meillo@63: .P
meillo@76: Finally, there's
meillo@76: .Pn slocal .
meillo@76: .Pn slocal
meillo@76: is an MDA and thus not directly MUA-related.
meillo@78: It should be removed, because including it is a violation
meillo@78: of the idea that mmh is a MUA only.
meillo@78: It should become a separate project.
meillo@87: However,
meillo@76: .Pn slocal
meillo@76: provides rule-based processing of messages, like filing them into
meillo@76: different folders, which is otherwise not available in mmh.
meillo@87: Although
meillo@76: .Pn slocal
meillo@87: does neither pull in dependencies nor does it include a separate
meillo@87: technical area (cf. Sec. XXX),
meillo@87: still it accounts for about 1\|000 lines of code that need to be maintained.
meillo@76: As
meillo@76: .Pn slocal
meillo@76: is almost self-standing, it should be split off into a separate project.
meillo@76: This would cut the strong connection between the MUA mmh and the MDA
meillo@76: .Pn slocal .
meillo@87: For anyone not using MH,
meillo@87: .Pn slocal
meillo@87: would become yet another independent MDA, like
meillo@87: .I procmail .
meillo@87: The need to install a complete MH system to have
meillo@87: .Pn slocal
meillo@87: would be gone.
meillo@76: Likewise, mmh users could decide to use
meillo@76: .I procmail
meillo@87: without having a second, unused MDA,
meillo@87: .Pn slocal ,
meillo@76: installed.
meillo@76: That's conceptionally the best solution.
meillo@76: Yet,
meillo@76: .Pn slocal
meillo@87: is not split off.
meillo@87: I feel unsure with removing it from mmh.
meillo@87: Hence, I defer the decision over
meillo@87: .Pn slocal .
meillo@87: In the meanwhile
meillo@78: .Pn slocal
meillo@87: does not hurt because it is unrelated to the rest of mmh.
meillo@0: 
meillo@58: 
meillo@76: .H2 "\fLshow\fP and \fPmhshow\fP
meillo@58: .P
meillo@69: Since the very beginning \(en already in the first concept paper \(en
meillo@58: .Pn show
meillo@62: had been MH's message display program.
meillo@58: .Pn show
meillo@76: mapped message numbers and sequences to files and invoked
meillo@58: .Pn mhl
meillo@76: to have the files formated.
meillo@88: With MIME, this approach wasn't sufficient anymore.
meillo@58: MIME messages can consist of multiple parts, some of which aren't
meillo@88: directly displayable, further more text content might be encoded in
meillo@58: foreign charsets.
meillo@58: .Pn show 's
meillo@76: understanding of messages and
meillo@58: .Pn mhl 's
meillo@88: display capabilities couldn't cope with the task any longer.
meillo@62: .P
meillo@88: Instead of extending these tools, additional tools were written from
meillo@88: scratch and added to the MH tool chest.
meillo@88: Doing so is encouraged by the tool chest approach.
meillo@88: Modular design is a great advantage for extending a system,
meillo@88: as new tools can be added without interfering with existing ones.
meillo@62: First, the new MIME features were added in form of the single program
meillo@58: .Pn mhn .
meillo@58: The command
meillo@82: .Cl "mhn -show 42
meillo@58: would show the MIME message numbered 42.
meillo@58: With the 1.0 release of nmh in February 1999, Richard Coleman finished
meillo@58: the split of
meillo@58: .Pn mhn
meillo@88: into a set of specialized tools, which together covered the
meillo@88: multiple aspects of MIME.
meillo@88: One of them was
meillo@69: .Pn mhshow ,
meillo@88: which replaced
meillo@88: .Cl "mhn -show" .
meillo@88: It was capable of displaying MIME messages appropriately.
meillo@62: .P
meillo@88: From then on, two message display tools were part of nmh,
meillo@76: .Pn show
meillo@76: and
meillo@76: .Pn mhshow .
meillo@88: To ease the life of users,
meillo@69: .Pn show
meillo@69: was extended to automatically hand the job over to
meillo@69: .Pn mhshow
meillo@69: if displaying the message would be beyond
meillo@69: .Pn show 's
meillo@69: abilities.
meillo@88: In consequence, the user would simply invoke
meillo@69: .Pn show
meillo@69: (possibly through
meillo@69: .Pn next
meillo@69: or
meillo@69: .Pn prev )
meillo@69: and get the message printed with either
meillo@69: .Pn show
meillo@69: or
meillo@69: .Pn mhshow ,
meillo@69: whatever was more appropriate.
meillo@69: .P
meillo@69: Having two similar tools for essentially the same task is redundant.
meillo@88: Usually,
meillo@88: users wouldn't distinguish between
meillo@88: .Pn show
meillo@88: and
meillo@88: .Pn mhshow
meillo@88: in their daily mail reading.
meillo@88: Having two separate display programs was therefore mainly unnecessary
meillo@88: from a user's point of view.
meillo@88: Besides, the development of both programs needed to be in sync,
meillo@76: to ensure that the programs behaved in a similar way,
meillo@76: because they were used like a single tool.
meillo@76: Different behavior would have surprised the user.
meillo@69: .P
meillo@69: Today, non-MIME messages are rather seen to be a special case of
meillo@88: MIME messages, although it's the other way round.
meillo@69: As
meillo@69: .Pn mhshow
meillo@88: had already be able to display non-MIME messages, it appeared natural
meillo@69: to drop
meillo@69: .Pn show
meillo@69: in favor of using
meillo@69: .Pn mhshow
meillo@69: exclusively.
meillo@88: .Ci 4c1efddfd499300c7e74263e57d8aa137e84c853
meillo@88: Removing
meillo@88: .Pn show
meillo@88: is no loss in function, because functionally
meillo@88: .Pn mhshow
meillo@88: covers it completely.
meillo@88: The old behavior of
meillo@88: .Pn show
meillo@88: can still be emulated with the simple command line:
meillo@88: .VS
meillo@88: mhl `mhpath c`
meillo@88: VE
meillo@88: .P
meillo@76: For convenience,
meillo@76: .Pn mhshow
meillo@88: was renamed to
meillo@88: .Pn show
meillo@88: after
meillo@88: .Pn show
meillo@88: was gone.
meillo@88: It is clear that such a rename may confuse future developers when
meillo@88: trying to understand the history.
meillo@88: Nevertheless, I consider the convenience on the user's side,
meillo@88: to call
meillo@88: .Pn show
meillo@88: when they want a message to be displayed, to outweigh the inconvenience
meillo@88: on the developer's side when understanding the project history.
meillo@69: .P
meillo@88: To prepare for the transition,
meillo@69: .Pn mhshow
meillo@69: was reworked to behave more like
meillo@69: .Pn show
meillo@69: first.
meillo@88: (cf. Sec. XXX)
meillo@88: Once the tools behaved more alike, the replacing appeared to be
meillo@88: even more natural.
meillo@88: Today, mmh's new
meillo@69: .Pn show
meillo@88: became the one single message display program again, with the difference
meillo@88: that today it handles MIME messages as well as non-MIME messages.
meillo@88: The outcome of the transition is one program less to maintain,
meillo@88: no second display program for users to deal with,
meillo@88: and less system complexity.
meillo@69: .P
meillo@88: Still, removing the old
meillo@69: .Pn show
meillo@88: hurts in one regard: It had been such a simple program.
meillo@88: Its lean elegance is missing to the new
meillo@69: .Pn show .
meillo@88: But there is no chance;
meillo@88: supporting MIME demands for higher essential complexity.
meillo@58: 
meillo@58: 
meillo@58: .H2 "Removal of Configure Options
meillo@58: .P
meillo@76: Customization is a double-edged sword.
meillo@76: It allows better suiting setups, but not for free.
meillo@76: There is the cost of code complexity to be able to customize.
meillo@76: There is the cost of less tested setups, because there are
meillo@72: more possible setups and especially corner-cases.
meillo@76: And, there is the cost of choice itself.
meillo@76: The code complexity directly affects the developers.
meillo@72: Less tested code affects both, users and developers.
meillo@76: The problem of choice affects the users, for once by having to
meillo@76: choose, but also by complexer interfaces that require more documentation.
meillo@72: Whenever options add little advantages, they should be considered for
meillo@72: removal.
meillo@72: I have reduced the number of project-specific configure options from 
meillo@72: fifteen to three.
meillo@74: 
meillo@76: .U3 "Mail Transfer Facilities
meillo@74: .P
meillo@85: With the removal of the mail transfer facilities five configure
meillo@85: options vanished:
meillo@85: .P
meillo@85: The switches
meillo@85: .Sw --with-tls
meillo@85: and
meillo@85: .Sw --with-cyrus-sasl
meillo@85: had activated the support for transfer encryption and authetication.
meillo@85: This is not needed anymore.
meillo@85: .Ci fecd5d34f65597a4dfa16aeabea7d74b191532c3
meillo@85: .Ci 156d35f6425bea4c1ed3c4c79783dc613379c65b
meillo@85: .P
meillo@85: The configure switch
meillo@85: .Sw --enable-pop
meillo@85: activated the message retrieval facility.
meillo@85: The code area that would be conditionally compiled in for TLS and SASL
meillo@85: support had been small.
meillo@85: The conditionally compiled code area for POP support had been much larger.
meillo@85: Whereas the code base changes would only slightly change on toggling
meillo@85: TLS or SASL support, it changed much on toggling POP support.
meillo@85: The changes in the code base could hardly be overviewed.
meillo@85: By having POP support togglable a second code base had been created,
meillo@85: one that needed to be tested.
meillo@85: This situation is basically similar for the conditional TLS and SASL  
meillo@85: code, but there the changes are minor and can yet be overviewed.
meillo@85: Still, conditional compilation of a code base creates variations
meillo@85: of the original program.
meillo@85: More variations require more testing and maintenance work.
meillo@85: .P
meillo@85: Two other options only specified default configuration values:
meillo@85: .Sw --with-mts=[smtp|sendmail]
meillo@85: defined the default transport service.
meillo@85: In mmh this fixed to
meillo@85: .Ar sendmail .
meillo@85: .Ci f6aa95b724fd8c791164abe7ee5468bf5c34f226
meillo@85: With
meillo@85: .Sw --with-smtpservers=[server1...]
meillo@85: default SMTP servers for the
meillo@85: .Ar smtp
meillo@85: transport service could be specified.
meillo@72: .Ci 128545e06224233b7e91fc4c83f8830252fe16c9
meillo@85: Both of them became irrelevant.
meillo@72: 
meillo@74: .U3 "Backup Prefix
meillo@74: .P
meillo@76: The backup prefix is the string that was prepended to message
meillo@76: filenames to tag them as deleted.
meillo@76: By default it had been the comma character `\f(CW,\fP'.
meillo@78: In July 2000, Kimmo Suominen introduced
meillo@78: the configure option
meillo@78: .Sw --with-hash-backup
meillo@78: to change the default to the hash symbol `\f(CW#\fP'.
meillo@78: The choice was probably personal preference, because first, the
meillo@78: option was named
meillo@78: .Sw --with-backup-prefix.
meillo@78: and had the prefix symbol as argument.
meillo@78: Because giving the hash symbol as argument caused to many problems
meillo@78: for configure,
meillo@78: the option was limited to use the hash symbol as the default prefix.
meillo@78: This makes me believe, that the choice for the hash was personal preference.
meillo@78: Being it related or not, words that start with the hash symbol
meillo@78: introduce a comment in the Unix shell.
meillo@72: Thus, the command line
meillo@72: .Cl "rm #13 #15
meillo@72: calls
meillo@72: .Pn rm
meillo@72: without arguments because the first hash symbol starts the comment
meillo@72: that reaches until the end of the line.
meillo@72: To delete the backup files,
meillo@72: .Cl "rm ./#13 ./#15"
meillo@72: needs to be used.
meillo@78: Using the hash as backup prefix can be seen as a precaution agains
meillo@78: data loss.
meillo@78: .P
meillo@72: I removed the configure option but added the profile entry
meillo@72: .Pe backup-prefix ,
meillo@72: which allows to specify an arbitrary string as backup prefix.
meillo@72: .Ci 6c40d481d661d532dd527eaf34cebb6d3f8ed086
meillo@76: Profile entries are the common method to change mmh's behavior.
meillo@76: This change did not remove the choice but moved it to a location where
meillo@72: it suited better.
meillo@76: .P
meillo@78: Eventually, however, the new trash folder concept
meillo@78: .Cf "Sec. XXX
meillo@78: obsoleted the concept of the backup prefix completely.
meillo@78: .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@72: (Well, there still are corner-cases to remove until the backup
meillo@72: prefix can be layed to rest, eventually.)
meillo@72: .\" FIXME: Do this work in the code!
meillo@76: 
meillo@76: .U3 "Editor and Pager
meillo@74: .P
meillo@74: The two configure options
meillo@74: .CW --with-editor=EDITOR
meillo@74: .CW --with-pager=PAGER
meillo@74: were used to specify the default editor and pager at configure time.
meillo@74: Doing so at configure time made sense in the Eighties,
meillo@76: when the set of available editors and pagers varied much across
meillo@76: different systems.
meillo@76: Today, the situation is more homegeneic.
meillo@74: The programs
meillo@74: .Pn vi
meillo@74: and
meillo@74: .Pn more
meillo@76: can be expected to be available on every Unix system,
meillo@74: as they are specified by POSIX since two decades.
meillo@74: (The specifications for
meillo@74: .Pn vi
meillo@74: and
meillo@74: .Pn more
meillo@74: appeared in
meillo@74: .[
meillo@74: posix 1987
meillo@74: .]
meillo@74: and,
meillo@74: .[
meillo@74: posix 1992
meillo@74: .]
meillo@74: respectively.)
meillo@74: As a first step, these two tools were hard-coded as defaults.
meillo@74: .Ci 5d43a99db70c12a673028c7758c20cbe3e13ef5f
meillo@74: Not changed were the
meillo@74: .Pe editor
meillo@74: and
meillo@74: .Pe moreproc
meillo@76: profile entries, which allowed the user to override the system defaults.
meillo@74: Later, the concept was reworked to respect the standard environment
meillo@74: variables
meillo@74: .Ev VISUAL
meillo@74: and
meillo@74: .Ev PAGER
meillo@76: if they are set.
meillo@74: Today, mmh determines the editor to use in the following order,
meillo@74: taking the first available and non-empty item:
meillo@74: .IP (1)
meillo@74: Environment variable
meillo@74: .Ev MMHEDITOR
meillo@74: .IP (2)
meillo@74: Profile entry
meillo@74: .Pe Editor
meillo@74: .IP (3)
meillo@74: Environment variable
meillo@74: .Ev VISUAL
meillo@74: .IP (4)
meillo@74: Environment variable
meillo@74: .Ev EDITOR
meillo@74: .IP (5)
meillo@74: Command
meillo@74: .Pn vi .
meillo@74: .P
meillo@76: .Ci f85f4b7ae62e3d05a945dcd46ead51f0a2a89a9b
meillo@76: .P
meillo@76: The pager to use is deteminded in a similar order,
meillo@74: also taking the first available and non-empty item:
meillo@74: .IP (1)
meillo@74: Environment variable
meillo@74: .Ev MMHPAGER
meillo@74: .IP (2)
meillo@74: Profile entry
meillo@74: .Pe Pager
meillo@74: (replaces
meillo@74: .Pe moreproc )
meillo@74: .IP (3)
meillo@74: Environment variable
meillo@74: .Ev PAGER
meillo@74: .IP (4)
meillo@74: Command
meillo@74: .Pn more .
meillo@74: .P
meillo@74: .Ci 0c4214ea2aec6497d0d67b436bbee9bc1d225f1e
meillo@74: .P
meillo@76: By respecting the
meillo@74: .Ev VISUAL /\c
meillo@74: .Ev EDITOR
meillo@74: and
meillo@74: .Ev PAGER
meillo@76: environment variables,
meillo@76: the new behavior confirms better to the common style on Unix systems.
meillo@76: Additionally, the new approach is more uniform and clearer to users.
meillo@72: 
meillo@74: .U3 "Locale
meillo@74: .P
meillo@74: The configure option
meillo@74: .Sw --disable-locale
meillo@85: was removed because POSIX provides locale support and there's
meillo@85: hardly any need to disable locale support.
meillo@74: .Ci ccf4f175ef4c4e7522f9510a4a1149c15d810dd9
meillo@72: 
meillo@76: .U3 "ndbm
meillo@72: .P
meillo@74: .Pn slocal
meillo@78: used to depend on
meillo@74: .I ndbm ,
meillo@74: a database library.
meillo@76: The database is used to store the `\fLMessage-ID\fP's of all
meillo@76: messages delivered.
meillo@74: This enables
meillo@74: .Pn slocal
meillo@74: to suppress delivering the same message to the same user twice.
meillo@74: (This features was enabled by the
meillo@74: .Sw -suppressdup
meillo@74: switch.)
meillo@74: .P
meillo@74: A variety of version of the database library exist.
meillo@78: .[
meillo@78: wolter unix incompat notes dbm
meillo@78: .]
meillo@74: Complicated autoconf code was needed to detect them correctly.
meillo@74: Further more, the configure switches
meillo@74: .Sw --with-ndbm=ARG
meillo@74: and
meillo@74: .Sw --with-ndbmheader=ARG
meillo@74: were added to help with difficult setups that would
meillo@78: not be detected automatically or correctly.
meillo@74: .P
meillo@74: By removing the suppress duplicates feature of
meillo@74: .Pn slocal ,
meillo@74: the dependency on
meillo@74: .I ndbm
meillo@78: vanished and 120 lines of complex autoconf code could be saved.
meillo@74: .Ci ecd6d6a20cb7a1507e3a20d6c4cb3a1cf14c6bbf
meillo@78: The change removed funtionality too, but that is minor to the
meillo@78: improvement by dropping the dependency and the complex autoconf code.
meillo@72: 
meillo@74: .U3 "mh-e Support
meillo@72: .P
meillo@74: The configure option
meillo@74: .Sw --disable-mhe
meillo@74: was removed when the mh-e support was reworked. 
meillo@74: Mh-e is the Emacs front-end to MH.
meillo@76: It requires MH to provide minor additional functions.
meillo@76: The
meillo@76: .Sw --disable-mhe
meillo@76: configure option could switch these extensions off.
meillo@76: After removing the support for old versions of mh-e,
meillo@74: only the
meillo@74: .Sw -build
meillo@76: switches of
meillo@74: .Pn forw
meillo@74: and
meillo@74: .Pn repl
meillo@76: are left to be mh-e extensions.
meillo@76: They are now always built in because they add little code and complexity.
meillo@76: In consequence, the
meillo@74: .Sw --disable-mhe
meillo@76: configure option was removed
meillo@72: .Ci a7ce7b4a580d77b6c2c4d980812beb589aa4c643
meillo@74: Removing the option removed a second code setup that would have
meillo@74: needed to be tested.
meillo@76: This change was first done in nmh and thereafter merged into mmh.
meillo@76: .P
meillo@76: The interface changes in mmh require mh-e to be adjusted in order
meillo@76: to be able to use mmh as back-end.
meillo@76: This will require minor changes to mh-e, but removing the
meillo@76: .Sw -build
meillo@76: switches would require more rework.
meillo@72: 
meillo@74: .U3 "Masquerading
meillo@72: .P
meillo@74: The configure option
meillo@74: .Sw --enable-masquerade
meillo@76: could take up to three arguments:
meillo@76: `draft_from', `mmailid', and `username_extension'.
meillo@74: They activated different types of address masquerading.
meillo@74: All of them were implemented in the SMTP-speaking
meillo@74: .Pn post
meillo@76: command, which provided an MSA.
meillo@76: Address masquerading is an MTA's task and mmh does not cover
meillo@76: this field anymore.
meillo@76: Hence, true masquerading needs to be implemented in the external MTA.
meillo@74: .P
meillo@74: The
meillo@74: .I mmailid
meillo@74: masquerading type is the oldest one of the three and the only one
meillo@74: available in the original MH.
meillo@74: It provided a
meillo@74: .I username
meillo@74: to
meillo@74: .I fakeusername
meillo@76: mapping, based on the password file's GECOS field.
meillo@74: The man page
meillo@74: .Mp mh-tailor(5)
meillo@74: described the use case as being the following:
meillo@74: .QP
meillo@74: This is useful if you want the messages you send to always
meillo@74: appear to come from the name of an MTA alias rather than your
meillo@74: actual account name.  For instance, many organizations set up
meillo@74: `First.Last' sendmail aliases for all users.  If this is
meillo@74: the case, the GECOS field for each user should look like:
meillo@74: ``First [Middle] Last <First.Last>''
meillo@74: .P
meillo@74: As mmh sends outgoing mail via the local MTA only,
meillo@76: the best location to do such global rewrites is there.
meillo@74: Besides, the MTA is conceptionally the right location because it
meillo@74: does the reverse mapping for incoming mail (aliasing), too.
meillo@76: Further more, masquerading set up there is readily available for all
meillo@74: mail software on the system.
meillo@76: Hence, mmailid masquerading was removed.
meillo@74: .Ci 0836c8000ccb34b59410ef1c15b1b7feac70ce5f
meillo@74: .P
meillo@74: The
meillo@74: .I username_extension
meillo@76: masquerading type did not replace the username but would append a suffix,
meillo@76: specified by the
meillo@74: .Ev USERNAME_EXTENSION
meillo@76: environment variable, to it.
meillo@76: This provided support for the
meillo@74: .I user-extension
meillo@74: feature of qmail and the similar
meillo@74: .I "plussed user
meillo@74: processing of sendmail.
meillo@74: The decision to remove this username_extension masquerading was
meillo@74: motivated by the fact that
meillo@74: .Pn spost
meillo@76: hadn't supported it already.
meillo@76: .Ci 2abae0bfd0ad5bf898461e50aa4b466d641f23d9
meillo@76: Username extensions are possible in mmh, but less convenient to use.
meillo@76: .\" XXX format file %(getenv USERNAME_EXTENSION)
meillo@74: .P
meillo@74: The
meillo@74: .I draft_from
meillo@74: masquerading type instructed
meillo@74: .Pn post
meillo@84: to use the value of the
meillo@84: .Hd From
meillo@84: header field as SMTP envelope sender.
meillo@76: Sender addresses could be replaced completely.
meillo@74: .Ci b14ea6073f77b4359aaf3fddd0e105989db9
meillo@76: Mmh offers a kind of masquerading similar in effect, but
meillo@74: with technical differences.
meillo@76: As mmh does not transfer messages itself, the local MTA has final control
meillo@76: over the sender's address. Any masquerading mmh introduces may be reverted
meillo@76: by the MTA.
meillo@76: In times of pedantic spam checking, an MTA will take care to use
meillo@76: sensible envelope sender addresses to keep its own reputation up.
meillo@84: Nonetheless, the MUA can set the
meillo@84: .Hd From
meillo@84: header field and thereby propose
meillo@76: a sender address to the MTA.
meillo@74: The MTA may then decide to take that one or generate the canonical sender
meillo@74: address for use as envelope sender address.
meillo@74: .P
meillo@74: In mmh, the MTA will always extract the recipient and sender from the
meillo@84: message header (\c
meillo@74: .Pn sendmail 's
meillo@74: .Sw -t
meillo@74: switch).
meillo@84: The
meillo@84: .Hd From
meillo@84: header field of the draft may be set arbitrary by the user.
meillo@74: If it is missing, the canonical sender address will be generated by the MTA.
meillo@74: 
meillo@74: .U3 "Remaining Options
meillo@74: .P
meillo@74: Two configure options remain in mmh.
meillo@74: One is the locking method to use:
meillo@74: .Sw --with-locking=[dot|fcntl|flock|lockf] .
meillo@76: The idea of removing all methods except the portable dot locking
meillo@76: and having that one as the default is appealing, but this change
meillo@76: requires deeper technical investigation into the topic.
meillo@76: The other option,
meillo@74: .Sw --enable-debug ,
meillo@74: compiles the programs with debugging symbols and does not strip them.
meillo@74: This option is likely to stay.
meillo@72: 
meillo@72: 
meillo@58: 
meillo@63: 
meillo@58: .H2 "Removal of switches
meillo@58: .P
meillo@58: 
meillo@58: 
meillo@58: 
meillo@58: 
meillo@74: .H1 "Modernizing
meillo@58: 
meillo@58: 
meillo@58: .H2 "Removal of Code Relicts
meillo@0: .P
meillo@51: The code base of mmh originates from the late Seventies,
meillo@51: had been extensively
meillo@51: worked on in the mid Eighties, and had been partly reorganized and extended
meillo@51: in the Nineties. Relicts of all those times had gathered in the code base.
meillo@12: My goal was to remove any ancient code parts. One part of the task was
meillo@12: converting obsolete code constructs to standard constructs, the other part
meillo@12: was dropping obsolete functions.
meillo@12: .P
meillo@12: As I'm not even thirty years old and have no more than seven years of
meillo@51: Unix experience, I needed to learn about the history in retrospective.
meillo@51: Older people likely have used those ancient constructs themselves
meillo@51: and have suffered from their incompatibilities and have longed for
meillo@12: standardization. Unfortunately, I have only read that others had done so.
meillo@12: This put me in a much more difficult positions when working on the old
meillo@12: code. I needed to recherche what other would have known by heart from
meillo@12: experience. All my programming experience comes from a time past ANSI C
meillo@12: and past POSIX. Although I knew about the times before, I took the
meillo@51: current state implicitly for granted most of the time.
meillo@12: .P
meillo@12: Being aware of
meillo@12: these facts, I rather let people with more historic experience solve the 
meillo@12: task of converting the ancient code constructs to standardized ones.
meillo@12: Luckily, Lyndon Nerenberg focused on this task at the nmh project.
meillo@12: He converted large parts of the code to POSIX constructs, removing
meillo@12: the conditionals compilation for now standardized features.
meillo@12: I'm thankful for this task being solved. I only pulled the changes into
meillo@12: mmh.
meillo@12: .P
meillo@20: The other task \(en dropping ancient functionality to remove old code \(en
meillo@12: I did myself, though. My position to strip mmh to the bare minimum of
meillo@12: frequently used features is much more revolutional than the nmh community
meillo@20: likes it. Without the need to justify my decisions, I was able to quickly
meillo@20: remove functionality I considered ancient.
meillo@20: The need to discuss my decisions with
meillo@20: peers likely would have slowed this process down. Of course, I researched
meillo@12: if a particular feature really should be dropped. Having not had any
meillo@12: contact to this feature within my computer life was a first indicator to
meillo@12: drop it, but I also asked others and searched the literature for modern
meillo@12: usage of the feature. If it appeared to be truly ancient, I dropped it.
meillo@12: The reason for dropping is always part of the commit message in the
meillo@12: version control system. Thus, it is easy for others to check their
meillo@12: view on the topic with mine and possibly to argue for reinclusion.
meillo@12: 
meillo@12: .U2 "MMDF maildrop support
meillo@12: .P
meillo@12: I did drop any support for the MMDF maildrop format. This type of format
meillo@12: is conceptionally similar to the mbox format, but uses four bytes with
meillo@12: value 1 (\fL^A^A^A^A\fP) as message delimiter,
meillo@18: instead of the string ``\fLFrom\ \fP''.
meillo@12: Due to the similarity and mbox being the de-facto standard maildrop
meillo@12: format on Unix, but also due to the larger influence of Sendmail than MMDF,
meillo@12: the MMDF maildrop format had vanished.
meillo@12: .P
meillo@12: The simplifications within the code were only moderate. Switches could
meillo@12: be removed from tools like
meillo@12: .L packf ,
meillo@12: which generate packed mailboxes. Only one packed mailbox format remained:
meillo@12: mbox.
meillo@12: The most important changes affect the equally named mail parsing routine in
meillo@12: .L sbr/m_getfld.c .
meillo@12: The direct MMDF code had been removed, but as now only one packed mailbox
meillo@12: format is left, code structure simplifications are likely possible.
meillo@12: The reason why they are still outstanding is the heavily optimized code
meillo@18: of
meillo@18: .Fu m_getfld() .
meillo@18: Changes beyond a small local scope \(en
meillo@12: which restructuring in its core is \(en cause a high risk of damaging
meillo@12: the intricate workings of the optimized code. This problem is know
meillo@12: to the developers of nmh, too. They also avoid touching this minefield
meillo@12: if possible.
meillo@12: 
meillo@12: .U2 "UUCP Bang Paths
meillo@12: .P
meillo@12: More questionably than the former topic is the removal of support for the
meillo@12: UUCP bang path address style. However, the user may translate the bang
meillo@12: paths on retrieval to Internet addresses and the other way on posting
meillo@12: messages. The former can be done my an MDA like procmail; the latter
meillo@12: by a sendmail wrapper. This would ensure that any address handling would
meillo@12: work as expected. However, it might just work well without any
meillo@12: such modifications, as mmh does not touch addresses much, in general.
meillo@12: But I can't ensure as I have never used an environment with bang paths.
meillo@12: Also, the behavior might break at any point in further development.
meillo@12: 
meillo@12: .U2 "Hardcopy terminal support
meillo@12: .P
meillo@12: More of a funny anecdote is the remaining of a check for printing to a
meillo@12: hardcopy terminal until Spring 2012, when I finally removed it.
meillo@12: I surely would be very happy to see such a terminal in action, maybe
meillo@12: actually being able to work on it, but I fear my chances are null.
meillo@12: .P
meillo@12: The check only prevented a pager to be placed between the outputting
meillo@18: program (\c
meillo@18: .Pn mhl )
meillo@18: and the terminal. This could have been ensured with
meillo@18: the
meillo@82: .Sw -nomoreproc
meillo@18: at the command line statically, too.
meillo@12: 
meillo@12: .U2 "Removed support for header fields
meillo@12: .P
meillo@84: The
meillo@84: .Hd Encrypted
meillo@84: header field had been introduced by RFC\^822, but already
meillo@12: marked legacy in RFC 2822. It was superseded by FIXME.
meillo@84: Mmh does no more support this header field.
meillo@12: .P
meillo@84: Native support for
meillo@84: .Hd Face
meillo@84: header fields had been removed, as well.
meillo@84: The feature is similar to the
meillo@84: .Hd X-Face
meillo@84: header field in its intent,
meillo@21: but takes a different approach to store the image.
meillo@84: Instead of encoding the image data directly into the header field,
meillo@84: the it contains the hostname and UDP port where the image
meillo@21: date could be retrieved.
meillo@84: Neither
meillo@84: .Hd X-Face
meillo@84: nor the here described
meillo@84: .Hd Face
meillo@84: system
meillo@21: \**
meillo@21: .FS
meillo@21: There is also a newer but different system, invented 2005,
meillo@84: using
meillo@84: .Hd Face
meillo@84: headers.
meillo@84: It is the successor of
meillo@84: .Hd X-Face
meillo@84: providing colored PNG images.
meillo@21: .FE
meillo@21: became well used in the large scale.
meillo@21: It's still possible to use a Face systems,
meillo@21: although mmh does not provide support for any of the different systems
meillo@21: anymore. It's fairly easy to write a small shell script to 
meillo@21: extract the embedded or fetch the external Face data and display the image.
meillo@84: Own
meillo@84: .Hd Face
meillo@84: header field can be added into the draft template files.
meillo@21: .P
meillo@84: .Hd Content-MD5
meillo@84: header fields were introduced by RFC\^1864. They provide only
meillo@12: a verification of data corruption during the transfer. By no means can
meillo@12: they ensure verbatim end-to-end delivery of the contents. This is clearly
meillo@12: stated in the RFC. The proper approach to provide verificationability
meillo@12: of content in an end-to-end relationship is the use of digital cryptography
meillo@12: (RFCs FIXME). On the other hand, transfer protocols should ensure the
meillo@12: integrity of the transmission. In combinations these two approaches
meillo@84: make the
meillo@84: .Hd Content-MD5
meillo@84: header field useless. In consequence, I removed
meillo@12: the support for it. By this removal, MD5 computation is not needed
meillo@12: anywhere in mmh. Hence, over 500 lines of code were removed by this one
meillo@84: change. Even if the
meillo@84: .Hd Content-MD5
meillo@84: header field is useful sometimes,
meillo@12: I value its usefulnes less than the improvement in maintainability, caused
meillo@12: by the removal.
meillo@12: 
meillo@20: .U2 "Prompter's Control Keys
meillo@20: .P
meillo@20: The program
meillo@20: .Pn prompter
meillo@20: queries the user to fill in a message form. When used by
meillo@20: .Pn comp
meillo@20: as:
meillo@82: .VS
meillo@82: comp -editor prompter
meillo@82: VE
meillo@20: the resulting behavior is similar to
meillo@20: .Pn mailx .
meillo@51: Apparently,
meillo@20: .Pn prompter
meillo@20: hadn't been touched lately. Otherwise it's hardly explainable why it
meillo@20: still offered the switches
meillo@84: .Sw -erase
meillo@84: .Ar chr
meillo@20: and
meillo@84: .Sw -kill
meillo@84: .Ar chr
meillo@20: to name the characters for command line editing.
meillo@21: The times when this had been necessary are long time gone.
meillo@20: Today these things work out-of-the-box, and if not, are configured
meillo@20: with the standard tool
meillo@20: .Pn stty .
meillo@20: 
meillo@21: .U2 "Vfork and Retry Loops
meillo@21: .P
meillo@51: MH creates many processes, which is a consequence of the tool chest approach.
meillo@21: In earlier times
meillo@21: .Fu fork()
meillo@21: had been an expensive system call, as the process's whole image needed
meillo@21: to be duplicated. One common case is replacing the image with
meillo@21: .Fu exec()
meillo@21: right after having forked the child process.
meillo@21: To speed up this case, the
meillo@21: .Fu vfork()
meillo@21: system call was invented at Berkeley. It completely omits copying the
meillo@21: image. If the image gets replaced right afterwards then unnecessary
meillo@21: work is omited. On old systems this results in large speed ups.
meillo@21: MH uses
meillo@21: .Fu vfork()
meillo@21: whenever possible.
meillo@21: .P
meillo@21: Memory management units that support copy-on-write semantics make
meillo@21: .Fu fork()
meillo@21: almost as fast as
meillo@21: .Fu vfork()
meillo@21: in the cases when they can be exchanged.
meillo@21: With
meillo@21: .Fu vfork()
meillo@51: being more error-prone and hardly faster, it's preferable to simply
meillo@21: use
meillo@21: .Fu fork()
meillo@21: instead.
meillo@21: .P
meillo@21: Related to the costs of
meillo@21: .Fu fork()
meillo@21: is the probability of its success.
meillo@21: Today on modern systems, the system call will succeed almost always.
meillo@51: In the Eighties on heavy loaded systems, as they were common at
meillo@21: universities, this had been different. Thus, many of the
meillo@21: .Fu fork()
meillo@21: calls were wrapped into loops to retry to fork several times in
meillo@21: short intervals, in case of previous failure.
meillo@21: In mmh, the program aborts at once if the fork failed.
meillo@21: The user can reexecute the command then. This is expected to be a
meillo@21: very rare case on modern systems, especially personal ones, which are
meillo@21: common today.
meillo@21: 
meillo@12: 
meillo@58: .H2 "Attachments
meillo@22: .P
meillo@58: MIME
meillo@58: 
meillo@58: 
meillo@58: .H2 "Digital Cryptography
meillo@22: .P
meillo@58: Signing and encryption.
meillo@58: 
meillo@58: 
meillo@58: .H2 "Good Defaults
meillo@22: .P
meillo@58: foo
meillo@58: 
meillo@58: 
meillo@58: 
meillo@58: 
meillo@58: .H1 "Code style
meillo@22: .P
meillo@58: foo
meillo@58: 
meillo@58: 
meillo@58: .H2 "Standard Code
meillo@22: .P
meillo@58: POSIX
meillo@22: 
meillo@22: 
meillo@58: .H2 "Separation
meillo@14: 
meillo@58: .U2 "MH Directory Split
meillo@0: .P
meillo@19: In MH and nmh, a personal setup had consisted of two parts:
meillo@19: The MH profile, named
meillo@19: .Fn \&.mh_profile
meillo@19: and being located directly in the user's home directory.
meillo@19: And the MH directory, where all his mail messages and also his personal
meillo@19: forms, scan formats, other configuration files are stored. The location
meillo@19: of this directory could be user-chosen. The default was to name it
meillo@19: .Fn Mail
meillo@19: and have it directly in the home directory.
meillo@19: .P
meillo@19: I've never liked the data storage and the configuration to be intermixed.
meillo@19: They are different kinds of data. One part, are the messages,
meillo@19: which are the data to operate on. The other part, are the personal
meillo@19: configuration files, which are able to change the behavior of the operations.
meillo@19: The actual operations are defined in the profile, however.
meillo@19: .P
meillo@19: When storing data, one should try to group data by its type.
meillo@19: There's sense in the Unix file system hierarchy, where configuration
meillo@19: file are stored separate (\c
meillo@19: .Fn /etc )
meillo@19: to the programs (\c
meillo@19: .Fn /bin
meillo@19: and
meillo@19: .Fn /usr/bin )
meillo@19: to their sources (\c
meillo@19: .Fn /usr/src ).
meillo@19: Such separation eases the backup management, for instance.
meillo@19: .P
meillo@19: In mmh, I've reorganized the file locations.
meillo@19: Still there are two places:
meillo@19: There's the mail storage directory, which, like in MH, contains all the
meillo@19: messages, but, unlike in MH, nothing else.
meillo@19: Its location still is user-chosen, with the default name
meillo@19: .Fn Mail ,
meillo@19: in the user's home directory. This is much similar to the case in nmh.
meillo@19: The configuration files, however, are grouped together in the new directory
meillo@19: .Fn \&.mmh
meillo@19: in the user's home directory.
meillo@19: The user's profile now is a file, named
meillo@19: .Fn profile ,
meillo@19: in this mmh directory.
meillo@19: Consistently, the context file and all the personal forms, scan formats,
meillo@19: and the like, are also there.
meillo@19: .P
meillo@19: The naming changed with the relocation.
meillo@19: The directory where everything, except the profile, had been stored (\c
meillo@19: .Fn $HOME/Mail ),
meillo@19: used to be called \fIMH directory\fP. Now, this directory is called the
meillo@19: user's \fImail storage\fP. The name \fImmh directory\fP is now given to
meillo@19: the new directory
meillo@19: (\c
meillo@19: .Fn $HOME/.mmh ),
meillo@19: containing all the personal configuration files.
meillo@19: .P
meillo@19: The separation of the files by type of content is logical and convenient.
meillo@19: There are no functional differences as any possible setup known to me
meillo@19: can be implemented with both approaches, although likely a bit easier
meillo@19: with the new approach. The main goal of the change had been to provide
meillo@19: sensible storage locations for any type of personal mmh file.
meillo@19: .P
meillo@19: In order for one user to have multiple MH setups, he can use the
meillo@19: environment variable
meillo@19: .Ev MH
meillo@19: the point to a different profile file.
meillo@19: The MH directory (mail storage plus personal configuration files) is
meillo@19: defined by the
meillo@19: .Pe Path
meillo@19: profile entry.
meillo@19: The context file could be defined by the
meillo@19: .Pe context
meillo@19: profile entry or by the
meillo@19: .Ev MHCONTEXT
meillo@19: environment variable.
meillo@19: The latter is useful to have a distinct context (e.g. current folders)
meillo@19: in each terminal window, for instance.
meillo@19: In mmh, there are three environment variables now.
meillo@19: .Ev MMH
meillo@19: may be used to change the location of the mmh directory.
meillo@19: .Ev MMHP
meillo@19: and
meillo@19: .Ev MMHC
meillo@19: change the profile and context files, respectively.
meillo@19: Besides providing a more consistent feel (which simply is the result
meillo@19: of being designed anew), the set of personal configuration files can
meillo@19: be chosen independently from the profile (including mail storage location)
meillo@19: and context, now. Being it relevant for practical use or not, it
meillo@19: de-facto is an improvement. However, the main achievement is the
meillo@19: split between mail storage and personal configuration files.
meillo@17: 
meillo@0: 
meillo@58: .H2 "Modularization
meillo@0: .P
meillo@58: whatnowproc
meillo@0: .P
meillo@49: The \fIMH library\fP
meillo@49: .Fn libmh.a
meillo@49: collects a bunch of standard functions that many of the MH tools need,
meillo@49: like reading the profile or context files.
meillo@49: This doesn't hurt the separation.
meillo@49: 
meillo@58: 
meillo@58: .H2 "Style
meillo@58: .P
meillo@58: Code layout, goto, ...
meillo@58: 
meillo@58: 
meillo@58: 
meillo@58: 
meillo@58: .H1 "Concept Exploitation/Homogeniety
meillo@58: 
meillo@58: 
meillo@58: .H2 "Draft Folder
meillo@58: .P
meillo@58: Historically, MH provided exactly one draft message, named
meillo@58: .Fn draft
meillo@58: and
meillo@58: being located in the MH directory. When starting to compose another message
meillo@58: before the former one was sent, the user had been questioned whether to use,
meillo@58: refile or replace the old draft. Working on multiple drafts at the same time
meillo@58: was impossible. One could only work on them in alteration by refiling the
meillo@58: previous one to some directory and fetching some other one for reediting. 
meillo@58: This manual draft management needed to be done each time the user wanted
meillo@58: to switch between editing one draft to editing another.
meillo@58: .P
meillo@58: To allow true parallel editing of drafts, in a straight forward way, the
meillo@58: draft folder facility exists. It had been introduced already in July 1984
meillo@58: by Marshall T. Rose. The facility was deactivated by default.
meillo@58: Even in nmh, the draft folder facility remained deactivated by default.
meillo@58: At least, Richard Coleman added the man page
meillo@58: .Mp mh-draft(5)
meillo@58: to document
meillo@58: the feature well.
meillo@58: .P
meillo@58: The only advantage of not using the draft folder facility is the static
meillo@58: name of the draft file. This could be an issue for MH frontends like mh-e.
meillo@58: But as they likely want to provide working on multiple drafts in parallel,
meillo@58: the issue is only concerning compatibility. The aim of nmh to stay compatible
meillo@58: prevented the default activation of the draft folder facility.
meillo@58: .P
meillo@58: On the other hand, a draft folder is the much more natural concept than
meillo@58: a draft message. MH's mail storage consists of folders and messages,
meillo@58: the messages named with ascending numbers. A draft message breaks with this
meillo@58: concept by introducing a message in a file named
meillo@58: .Fn draft .
meillo@58: This draft
meillo@58: message is special. It can not be simply listed with the available tools,
meillo@58: but instead requires special switches. I.e. corner-cases were
meillo@58: introduced. A draft folder, in contrast, does not introduce such
meillo@58: corner-cases. The available tools can operate on the messages within that
meillo@58: folder like on any messages within any mail folders. The only difference
meillo@58: is the fact that the default folder for
meillo@58: .Pn send
meillo@58: is the draft folder,
meillo@58: instead of the current folder, like for all other tools.
meillo@58: .P
meillo@58: The trivial part of the change was activating the draft folder facility
meillo@58: by default and setting a default name for this folder. Obviously, I chose
meillo@58: the name
meillo@58: .Fn +drafts .
meillo@58: This made the
meillo@82: .Sw -draftfolder
meillo@58: and
meillo@82: .Sw -draftmessage
meillo@58: switches useless, and I could remove them.
meillo@58: The more difficult but also the part that showed the real improvement,
meillo@58: was updating the tools to the new concept.
meillo@82: .Sw -draft
meillo@58: switches could
meillo@58: be dropped, as operating on a draft message became indistinguishable to
meillo@58: operating on any other message for the tools.
meillo@58: .Pn comp
meillo@58: still has its
meillo@82: .Sw -use
meillo@58: switch for switching between its two modes: (1) Compose a new
meillo@58: draft, possibly by taking some existing message as a form. (2) Modify
meillo@58: an existing draft. In either case, the behavior of
meillo@58: .Pn comp is
meillo@58: deterministic. There is no more need to query the user. I consider this
meillo@58: a major improvement. By making
meillo@58: .Pn send
meillo@58: simply operate on the current
meillo@58: message in the draft folder by default, with message and folder both
meillo@58: overridable by specifying them on the command line, it is now possible
meillo@58: to send a draft anywhere within the storage by simply specifying its folder
meillo@58: and name.
meillo@58: .P
meillo@58: All theses changes converted special cases to regular cases, thus
meillo@58: simplifying the tools and increasing the flexibility.
meillo@58: 
meillo@58: 
meillo@58: .H2 "Trash Folder
meillo@58: .P
meillo@58: Similar to the situation for drafts is the situation for removed messages.
meillo@58: Historically, a message was deleted by renaming. A specific
meillo@58: \fIbackup prefix\fP, often comma (\c
meillo@58: .Fn , )
meillo@58: or hash (\c
meillo@58: .Fn # ),
meillo@58: being prepended to the file name. Thus, MH wouldn't recognize the file
meillo@58: as a message anymore, as only files whose name consists of digits only
meillo@58: are treated as messages. The removed messages remained as files in the
meillo@58: same directory and needed some maintenance job to truly delete them after
meillo@58: some grace time. Usually, by running a command similar to
meillo@82: .VS
meillo@82: find /home/user/Mail -ctime +7 -name ',*' | xargs rm
meillo@82: VE
meillo@58: in a cron job. Within the grace time interval
meillo@58: the original message could be restored by stripping the
meillo@58: the backup prefix from the file name. If however, the last message of
meillo@58: a folder is been removed \(en say message
meillo@58: .Fn 6
meillo@58: becomes file
meillo@58: .Fn ,6
meillo@58: \(en and a new message enters the same folder, thus the same
meillo@58: numbered being given again \(en in our case
meillo@58: .Fn 6
meillo@58: \(en, if that one
meillo@58: is removed too, then the backup of the former message gets overwritten.
meillo@58: Thus, the ability to restore removed messages does not only depend on
meillo@58: the ``sweeping cron job'' but also on the removing of further messages.
meillo@58: This is undesirable, because the real mechanism is hidden from the user
meillo@58: and the consequences of further removals are not always obvious.
meillo@58: Further more, the backup files are scattered within the whole mail
meillo@58: storage, instead of being collected at one place.
meillo@58: .P
meillo@58: To improve the situation, the profile entry
meillo@58: .Pe rmmproc
meillo@58: (previously named
meillo@58: .Pe Delete-Prog )
meillo@58: was introduced, very early.
meillo@58: It could be set to any command, which would care for the mail removal
meillo@58: instead of taking the default action, described above.
meillo@58: Refiling the to-be-removed files to some garbage folder was a common
meillo@58: example. Nmh's man page
meillo@58: .Mp rmm(1)
meillo@58: proposes
meillo@58: .Cl "refile +d
meillo@58: to move messages to the garbage folder and
meillo@58: .Cl "rm `mhpath +d all`
meillo@58: the empty the garbage folder.
meillo@58: Managing the message removal this way is a sane approach. It keeps
meillo@58: the removed messages in one place, makes it easy to remove the backup
meillo@58: files, and, most important, enables the user to use the tools of MH
meillo@58: itself to operate on the removed messages. One can
meillo@58: .Pn scan
meillo@58: them,
meillo@58: .Pn show
meillo@58: them, and restore them with
meillo@58: .Pn refile .
meillo@58: There's no more
meillo@58: need to use
meillo@58: .Pn mhpath
meillo@58: to switch over from MH tools to Unix tools \(en MH can do it all itself.
meillo@58: .P
meillo@58: This approach matches perfect with the concepts of MH, thus making
meillo@58: it powerful. Hence, I made it the default. And even more, I also
meillo@58: removed the old backup prefix approach, as it is clearly less powerful.
meillo@58: Keeping unused alternative in the code is a bad choice as they likely
meillo@58: gather bugs, by not being constantly tested. Also, the increased code
meillo@58: size and more conditions crease the maintenance costs. By strictly
meillo@58: converting to the trash folder approach, I simplified the code base.
meillo@58: .Pn rmm
meillo@58: calls
meillo@58: .Pn refile
meillo@58: internally to move the to-be-removed
meillo@58: message to the trash folder (\c
meillo@58: .Fn +trash
meillo@58: by default). Messages
meillo@58: there can be operated on like on any other message in the storage.
meillo@58: The sweep clean, one can use
meillo@82: .Cl "rmm -unlink +trash a" ,
meillo@58: where the
meillo@82: .Sw -unlink
meillo@58: switch causes the files to be truly unliked instead
meillo@58: of moved to the trash folder.
meillo@58: 
meillo@58: 
meillo@58: .H2 "Path Notations
meillo@58: .P
meillo@58: foo
meillo@58: 
meillo@58: 
meillo@58: .H2 "MIME Integration
meillo@58: .P
meillo@58: user-visible access to whole messages and MIME parts are inherently
meillo@58: different
meillo@58: 
meillo@58: 
meillo@58: .H2 "Of One Cast
meillo@58: .P