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@setfilename gnus-coding
@settitle Gnus Coding Style and Maintenance Guide
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@copying
Copyright @copyright{} 2004-2005, 2007-2012 Free Software
Foundation, Inc.

@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with the Front-Cover texts being ``A GNU Manual'',
and with the Back-Cover Texts as in (a) below.  A copy of the license
is included in the section entitled ``GNU Free Documentation License''.

(a) The FSF's Back-Cover Text is: ``You have the freedom to copy and
modify this GNU manual.''
@end quotation
@end copying


@titlepage
@title Gnus Coding Style and Maintenance Guide

@author by Reiner Steib  <Reiner.Steib@@gmx.de>

@insertcopying
@end titlepage

@c Obviously this is only a very rudimentary draft.  We put it in the
@c repository anyway hoping that it might annoy someone enough to fix
@c it.  ;-) Fixing only a paragraph also is appreciated.

@ifnottex
@node Top
@top Gnus Coding Style and Maintenance Guide
This manual describes @dots{}

@insertcopying
@end ifnottex

@menu
* Gnus Coding Style:: Gnus Coding Style
* Gnus Maintenance Guide:: Gnus Maintenance Guide
* GNU Free Documentation License::  The license for this documentation.
@end menu

@c @ref{Gnus Reference Guide, ,Gnus Reference Guide, gnus, The Gnus Newsreader}

@node Gnus Coding Style
@chapter Gnus Coding Style
@section Dependencies

The Gnus distribution contains a lot of libraries that have been written
for Gnus and used intensively for Gnus.  But many of those libraries are
useful on their own.  E.g., other Emacs Lisp packages might use the
@acronym{MIME} library @xref{Top, ,Top, emacs-mime, The Emacs MIME
Manual}.

@subsection General purpose libraries

@table @file

@item netrc.el
@file{.netrc} parsing functionality.
@c As of 2005-10-21...
There are no Gnus dependencies in this file.

@item format-spec.el
Functions for formatting arbitrary formatting strings.
@c As of 2005-10-21...
There are no Gnus dependencies in this file.

@item hex-util.el
Functions to encode/decode hexadecimal string.
@c As of 2007-08-25...
There are no Gnus dependencies in these files.
@end table

@subsection Encryption and security

@table @file
@item encrypt.el
File encryption routines
@c As of 2005-10-25...
There are no Gnus dependencies in this file.

@item password.el
Read passwords from user, possibly using a password cache.
@c As of 2005-10-21...
There are no Gnus dependencies in this file.

@item tls.el
TLS/SSL support via wrapper around GnuTLS
@c As of 2005-10-21...
There are no Gnus dependencies in this file.

@item pgg*.el
Glue for the various PGP implementations.
@c As of 2005-10-21...
There are no Gnus dependencies in these files.

@item sha1.el
SHA1 Secure Hash Algorithm.
@c As of 2007-08-25...
There are no Gnus dependencies in these files.
@end table

@subsection Networking

@table @file
@item dig.el
Domain Name System dig interface.
@c As of 2005-10-21...
There are no serious Gnus dependencies in this file.  Uses
@code{gnus-run-mode-hooks} (a wrapper function).

@item dns.el, dns-mode.el
Domain Name Service lookups.
@c As of 2005-10-21...
There are no Gnus dependencies in these files.
@end table

@subsection Mail and News related RFCs

@table @file
@item pop3.el
Post Office Protocol (RFC 1460) interface.
@c As of 2005-10-21...
There are no Gnus dependencies in this file.

@item imap.el
@acronym{IMAP} library.
@c As of 2005-10-21...
There are no Gnus dependencies in this file.

@item ietf-drums.el
Functions for parsing RFC822bis headers.
@c As of 2005-10-21...
There are no Gnus dependencies in this file.

@item rfc1843.el
HZ (rfc1843) decoding.  HZ is a data format for exchanging files of
arbitrarily mixed Chinese and @acronym{ASCII} characters.
@c As of 2005-10-21...
@code{rfc1843-gnus-setup} seem to be useful only for Gnus.  Maybe this
function should be relocated to remove dependencies on Gnus.  Other
minor dependencies: @code{gnus-newsgroup-name} could be eliminated by
using an optional argument to @code{rfc1843-decode-article-body}.

@item rfc2045.el
Functions for decoding rfc2045 headers
@c As of 2007-08-25...
There are no Gnus dependencies in these files.

@item rfc2047.el
Functions for encoding and decoding rfc2047 messages
@c As of 2007-08-25...
There are no Gnus dependencies in these files.
@c
Only a couple of tests for gnusy symbols.

@item rfc2104.el
RFC2104 Hashed Message Authentication Codes
@c As of 2007-08-25...
There are no Gnus dependencies in these files.

@item rfc2231.el
Functions for decoding rfc2231 headers
@c As of 2007-08-25...
There are no Gnus dependencies in these files.

@item flow-fill.el
Interpret RFC2646 "flowed" text.
@c As of 2005-10-27...
There are no Gnus dependencies in this file.

@item uudecode.el
Elisp native uudecode.
@c As of 2005-12-06...
There are no Gnus dependencies in this file.
@c ... but the custom group is gnus-extract.

@item canlock.el
Functions for Cancel-Lock feature
@c Cf. draft-ietf-usefor-cancel-lock-01.txt
@c Although this draft has expired, Canlock-Lock revived in 2007 when
@c major news providers (e.g., news.individual.org) started to use it.
@c As of 2007-08-25...
There are no Gnus dependencies in these files.

@end table

@subsection message

All message composition from Gnus (both mail and news) takes place in
Message mode buffers.  Message mode is intended to be a replacement for
Emacs mail mode.  There should be no Gnus dependencies in
@file{message.el}.  Alas it is not anymore.  Patches and suggestions to
remove the dependencies are welcome.

@c message.el requires nnheader which requires gnus-util.

@subsection Emacs @acronym{MIME}

The files @file{mml*.el} and @file{mm-*.el} provide @acronym{MIME}
functionality for Emacs.

@acronym{MML} (@acronym{MIME} Meta Language) is supposed to be
independent from Gnus.  Alas it is not anymore.  Patches and suggestions
to remove the dependencies are welcome.

@subsection Gnus backends

The files @file{nn*.el} provide functionality for accessing NNTP
(@file{nntp.el}), IMAP (@file{nnimap.el}) and several other Mail back
ends (probably @file{nnml.el}, @file{nnfolder.el} and
@file{nnmaildir.el} are the most widely used mail back ends).

@c mm-uu requires nnheader which requires gnus-util.  message.el also
@c requires nnheader.


@section Compatibility

No Gnus and Gnus 5.10.10 and up should work on:
@itemize @bullet
@item
Emacs 21.1 and up.
@item
XEmacs 21.4 and up.
@end itemize

Gnus 5.10.8 and below should work on:
@itemize @bullet
@item
Emacs 20.7 and up.
@item
XEmacs 21.1 and up.
@end itemize

@node Gnus Maintenance Guide
@chapter Gnus Maintenance Guide

@section Stable and development versions

The development of Gnus normally is done on the Git repository trunk
as of April 19, 2010 (formerly it was done in CVS; the repository is
at http://git.gnus.org), i.e., there are no separate branches to
develop and test new features.  Most of the time, the trunk is
developed quite actively with more or less daily changes.  Only after
a new major release, e.g., 5.10.1, there's usually a feature period of
several months.  After the release of Gnus 5.10.6 the development of
new features started again on the trunk while the 5.10 series is
continued on the stable branch (v5-10) from which more stable releases
will be done when needed (5.10.8, @dots{}).  @ref{Gnus Development,
,Gnus Development, gnus, The Gnus Newsreader}

Stable releases of Gnus finally become part of Emacs.  E.g., Gnus 5.8
became a part of Emacs 21 (relabeled to Gnus 5.9).  The 5.10 series
became part of Emacs 22 as Gnus 5.11.

@section Syncing

@c Some MIDs related to this follow.  Use http://thread.gmane.org/MID
@c (and click on the subject) to get the thread on Gmane.

@c Some quotes from Miles Bader follow...

@c <v9eklyke6b.fsf@marauder.physik.uni-ulm.de>
@c <buovfd71nkk.fsf@mctpc71.ucom.lsi.nec.co.jp>

In the past, the inclusion of Gnus into Emacs was quite cumbersome.  For
each change made to Gnus in Emacs repository, it had to be checked that
it was applied to the new Gnus version, too.  Else, bug fixes done in
Emacs repository might have been lost.

With the inclusion of Gnus 5.10, Miles Bader has set up an Emacs-Gnus
gateway to ensure the bug fixes from Emacs CVS are propagated to Gnus
CVS semi-automatically.

After Emacs moved to bzr and Gnus moved to git, Katsumi Yamaoka has
taken over the chore of keeping Emacs and Gnus in sync.  In general,
changes made to one repository will usually be replicated in the other
within a few days.

Basically the idea is that the gateway will cause all common files in
Emacs and Gnus v5-13 to be identical except when there's a very good
reason (e.g., the Gnus version string in Emacs says @samp{5.11}, but
the v5-13 version string remains @samp{5.13.x}).  Furthermore, all
changes in these files in either Emacs or the v5-13 branch will be
installed into the Gnus git trunk, again except where there's a good
reason.

@c (typically so far the only exception has been that the changes
@c already exist in the trunk in modified form).
Because of this, when the next major version of Gnus will be included in
Emacs, it should be very easy -- just plonk in the files from the Gnus
trunk without worrying about lost changes from the Emacs tree.

The effect of this is that as hacker, you should generally only have to
make changes in one place:

@itemize
@item
If it's a file which is thought of as being outside of Gnus (e.g., the
new @file{encrypt.el}), you should probably make the change in the Emacs
tree, and it will show up in the Gnus tree a few days later.

If you don't have Emacs bzr access (or it's inconvenient), you can
change such a file in the v5-10 branch, and it should propagate to Emacs
bzr -- however, it will get some extra scrutiny (by Miles) to see if the
changes are possibly controversial and need discussion on the mailing
list.  Many changes are obvious bug-fixes however, so often there won't
be any problem.

@item
If it's to a Gnus file, and it's important enough that it should be part
of Emacs and the v5-10 branch, then you can make the change on the v5-10
branch, and it will go into Emacs bzr and the Gnus git trunk (a few days
later).  The most prominent examples for such changes are bug-fixed
including improvements on the documentation.

If you know that there will be conflicts (perhaps because the affected
source code is different in v5-10 and the Gnus git trunk), then you can
install your change in both places, and when I try to sync them, there
will be a conflict -- however, since in most such cases there would be a
conflict @emph{anyway}, it's often easier for me to resolve it simply if
I see two @samp{identical} changes, and can just choose the proper one,
rather than having to actually fix the code.

@item
For general Gnus development changes, of course you just make the
change on the Gnus Git trunk and it goes into Emacs a few years
later... :-)

@end itemize

Of course in any case, if you just can't wait for me to sync your
change, you can commit it in more than one place and probably there will
be no problem; usually the changes are textually identical anyway, so
can be easily resolved automatically (sometimes I notice silly things in
such multiple commits, like whitespace differences, and unify those ;-).


@c I do Emacs->Gnus less often (than Gnus->Emacs) because it tends to
@c require more manual work.

@c By default I sync about once a week.  I also try to follow any Gnus
@c threads on the mailing lists and make sure any changes being discussed
@c are kept more up-to-date (so say 1-2 days delay for "topical" changes).

@c <buovfd71nkk.fsf@mctpc71.ucom.lsi.nec.co.jp>

@c BTW, just to add even more verbose explanation about the syncing thing:

@section Miscellanea

@heading @file{GNUS-NEWS}

Starting from No Gnus, the @file{GNUS-NEWS} is created from
@file{texi/gnus-news.texi}.  Don't edit @file{GNUS-NEWS}.  Edit
@file{texi/gnus-news.texi}, type @command{make GNUS-NEWS} in the
@file{texi} directory and commit @file{GNUS-NEWS} and
@file{texi/gnus-news.texi}.

@heading Conventions for version information in defcustoms

For new customizable variables introduced in Oort Gnus (including the
v5-10 branch) use @code{:version "22.1" ;; Oort Gnus} (including the
comment) or, e.g., @code{:version "22.2" ;; Gnus 5.10.10} if the feature
was added for Emacs 22.2 and Gnus 5.10.10.
@c
If the variable is new in No Gnus use @code{:version "23.1" ;; No Gnus}.

The same applies for customizable variables when its default value was
changed.

@node GNU Free Documentation License
@appendix GNU Free Documentation License
@include doclicense.texi

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