* Information for Emacs Developers.
An "Emacs Developer" is someone who contributes a lot of code or
-documentation to the Emacs repository. Generally, they have write
+documentation to the Emacs repository. Generally, they have write
access to the Emacs git repository on Savannah
https://savannah.gnu.org/git/?group=emacs.
** Write access to the Emacs repository.
Once you become a frequent contributor to Emacs, we can consider
-giving you write access to the version-control repository. Request
-access on the emacs-devel@gnu.org mailing list.
+giving you write access to the version-control repository. Request
+access on the emacs-devel@gnu.org mailing list. Also, be sure to
+subscribe to the emacs-devel@gnu.org mailing list and include the
+"emacs-announce" topic, so that you get the announcements about
+feature freeze and other important events.
** Using the Emacs repository
-Emacs uses git for the source code repository.
+Emacs uses Git for the source code repository.
See http://www.emacswiki.org/emacs/GitQuickStartForEmacsDevs to get
started, and http://www.emacswiki.org/emacs/GitForEmacsDevs for more
Alternately, see admin/notes/git-workflow.
-If committing changes written by someone else, make the ChangeLog
-entry in their name, not yours. git distinguishes between the author
+If committing changes written by someone else, make the commit in
+their name, not yours. Git distinguishes between the author
and the committer; use the --author option on the commit command to
specify the actual author; the committer defaults to you.
-** commit messages
+** Commit messages
-When using git, commit messages should use ChangeLog format, with the
-following modifications:
+Emacs development no longer stores descriptions of new changes in
+ChangeLog files. Instead, a single ChangeLog file is generated from
+the commit messages when a release is prepared. So changes you commit
+should not touch any of the ChangeLog files in the repository, but
+instead should contain the log entries in the commit message. Here is
+an example of a commit message (indented):
-- Add a single short line explaining the change, then an empty line,
- then unindented ChangeLog entries.
+ Deactivate shifted region
- You can use various Emacs functions to ease this process; see (info
- "(emacs)Change Log Commands") or
- http://www.gnu.org/software/emacs/manual/html_node/emacs/Change-Log-Commands.html.
+ Do not silently extend a region that is not highlighted;
+ this can happen after a shift (Bug#19003).
+ * doc/emacs/mark.texi (Shift Selection): Document the change.
+ * lisp/window.el (handle-select-window):
+ * src/frame.c (Fhandle_switch_frame, Fselected_frame):
+ Deactivate the mark.
+
+Below are some rules and recommendations for formatting commit
+messages:
+
+- Start with a single unindented summary line explaining the change;
+ do not end this line with a period. If that line starts with a
+ semi-colon and a space "; ", the log message will be ignored when
+ generating the ChangeLog file. Use this for minor commits that do
+ not need separate ChangeLog entries, such as changes in etc/NEWS.
-- The summary line is limited to 72 characters (enforced by a commit
- hook). If you have trouble making that a good summary, add a
- paragraph below it, before the individual file descriptions.
+- After the summary line, there should be an empty line, then
+ unindented ChangeLog entries.
+
+- Limit lines in commit messages to 78 characters, unless they consist
+ of a single word of at most 140 characters; this is enforced by a
+ commit hook. It's nicer to limit the summary line to 50 characters;
+ this isn't enforced. If the change can't be summarized so briefly,
+ add a paragraph after the empty line and before the individual file
+ descriptions.
- If only a single file is changed, the summary line can be the normal
file first line (starting with the asterisk). Then there is no
individual files section.
+- If the commit has more than one author, the commit message should
+ contain separate lines to mention the other authors, like the
+ following:
+
+ Co-authored-by: Joe Schmoe <j.schmoe@example.org>
+
+- If the commit is a tiny change that is exempt from copyright paperwork,
+ the commit message should contain a separate line like the following:
+
+ Copyright-paperwork-exempt: yes
+
+- The commit message should contain "Bug#NNNNN" if it is related to
+ bug number NNNNN in the debbugs database. This string is often
+ parenthesized, as in "(Bug#19003)".
+
+- Commit messages should contain only printable UTF-8 characters.
+
+- Commit messages should not contain the "Signed-off-by:" lines that
+ are used in some other projects.
+
+- Any lines of the commit message that start with "; " are omitted
+ from the generated ChangeLog.
+
- Explaining the rationale for a design choice is best done in comments
- in the source code. However, sometimes it is useful to describe just
+ in the source code. However, sometimes it is useful to describe just
the rationale for a change; that can be done in the commit message
between the summary line and the file entries.
-** ChangeLog notes
-
- Emacs generally follows the GNU coding standards when it comes to
ChangeLogs:
- http://www.gnu.org/prep/standards/html_node/Change-Logs.html . One
- exception is that we still sometimes quote `like-this' (as the
- standards used to recommend) rather than 'like-this' (as they do
- now), because `...' is so widely used elsewhere in Emacs.
+ http://www.gnu.org/prep/standards/html_node/Change-Logs.html or
+ "(info (standards)Change Logs"). One exception is that we still
+ sometimes quote `like-this' (as the standards used to recommend)
+ rather than 'like-this' (as they do now), because `...' is so widely
+ used elsewhere in Emacs.
- Some of the rules in the GNU coding standards section 5.2
"Commenting Your Work" also apply to ChangeLog entries: they must be
ending with a period (except the summary line should not end in a
period).
- It is tempting to relax this rule for commit messages, since they
- are somewhat transient. However, they are preserved indefinitely,
- and have a reasonable chance of being read in the future, so it's
- better that they have good presentation.
-
-- There are multiple ChangeLogs in the emacs source; roughly one per
- high-level directory. The ChangeLog entry for a commit belongs in the
- lowest ChangeLog that is higher than or at the same level as any file
- changed by the commit.
+ They are preserved indefinitely, and have a reasonable chance of
+ being read in the future, so it's better that they have good
+ presentation.
- Use the present tense; describe "what the change does", not "what
the change did".
- Preferred form for several entries with the same content:
- * help.el (view-lossage):
- * kmacro.el (kmacro-edit-lossage):
- * edmacro.el (edit-kbd-macro): Fix docstring, lossage is now 300 keys.
+ * lisp/help.el (view-lossage):
+ * lisp/kmacro.el (kmacro-edit-lossage):
+ * lisp/edmacro.el (edit-kbd-macro): Fix docstring, lossage is now 300.
(Rather than anything involving "ditto" and suchlike.)
-- If the commit fixes a bug, add a separate line
-
- Fixes: bug#NNNN
-
- where NNNN is the bug number.
-
-- In ChangeLog entries, there is no standard or recommended way to
- identify revisions.
+- There is no standard or recommended way to identify revisions in
+ ChangeLog entries. Using Git SHA1 values limits the usability of
+ the references to Git, and will become much less useful if Emacs
+ switches to a different VCS. So we recommend against that.
One way to identify revisions is by quoting their summary line.
Another is with an action stamp - an RFC3339 date followed by !
followed by the committer's email - for example,
- "2014-01-16T05:43:35Z!esr@thyrsus.com". Often, "my previous commit"
+ "2014-01-16T05:43:35Z!esr@thyrsus.com". Often, "my previous commit"
will suffice.
-- There is no need to make separate ChangeLog entries for files such
- as NEWS, MAINTAINERS, and FOR-RELEASE, or to indicate regeneration
- of files such as 'configure'. "There is no need" means you don't
- have to, but you can if you want to.
+- There is no need to mention files such as NEWS and MAINTAINERS, or
+ to indicate regeneration of files such as 'configure', in the
+ ChangeLog entry. "There is no need" means you don't have to, but
+ you can if you want to.
-** branches
+** Generating ChangeLog entries
+
+- You can use various Emacs functions to ease the process of writing
+ ChangeLog entries; see (info "(emacs)Change Log Commands") or
+ http://www.gnu.org/software/emacs/manual/html_node/emacs/Change-Log-Commands.html.
+
+- If you use Emacs VC, one way to format ChangeLog entries is to create
+ a top-level ChangeLog file manually, and update it with 'C-x 4 a' as
+ usual. Do not register the ChangeLog file under git; instead, use
+ 'C-c C-a' to insert its contents into into your *vc-log* buffer.
+ Or if 'log-edit-hook' includes 'log-edit-insert-changelog' (which it
+ does by default), they will be filled in for you automatically.
+
+- Alternatively, you can use the vc-dwim command to maintain commit
+ messages. When you create a source directory, run the shell command
+ 'git-changelog-symlink-init' to create a symbolic link from
+ ChangeLog to .git/c/ChangeLog. Edit this ChangeLog via its symlink
+ with Emacs commands like 'C-x 4 a', and commit the change using the
+ shell command 'vc-dwim --commit'. Type 'vc-dwim --help' for more.
+
+** Branches
Development normally takes places on the trunk.
Sometimes specialized features are developed on separate branches
Development is discussed on the emacs-devel mailing list.
-Sometime before the release of a new major version of Emacs a "feature
-freeze" is imposed on the trunk, to prepare for creating a release
-branch. No new features may be added to the trunk after this point,
-until the release branch is created. Announcements about the freeze
-(and other important events) are made on the info-gnu-emacs mailing
-list, and not anywhere else.
-
The trunk branch is named "master" in git; release branches are named
"emacs-nn" where "nn" is the major version.
However, if you know that the change will be difficult to merge to the
trunk (eg because the trunk code has changed a lot), you can apply the
-change to both trunk and branch yourself. Indicate in the release
-branch commit log that there is no need to merge the commit to the
-trunk; start the commit message with "Backport:". gitmerge.el will
-then exclude that commit from the merge to trunk.
+change to both trunk and branch yourself. It could also happen that a
+change is cherry-picked from master to the release branch, and so
+doesn't need to be merged back. In these cases, indicate in the
+release branch commit log that there is no need to merge the commit to
+the trunk; start the commit message with "Backport:". gitmerge.el
+will then exclude that commit from the merge to trunk.
** Other process information
-See all the files in admin/notes/* . In particular, see
-admin/notes/newfile, see admin/notes/repo.
-
-*** git vs rename
-
-git does not explicitly represent a file renaming; it uses a percent
-changed heuristic to deduce that a file was renamed. So if you are
-planning to make extensive changes to a file after renaming it (or
-moving it to another directory), you should:
-
-- create a feature branch
-
-- commit the rename without any changes
-
-- make other changes
-
-- merge the feature branch to trunk, _not_ squashing the commits into
- one. The commit message on this merge should summarize the renames
- and all the changes.
-
** Emacs Mailing lists.
Discussion about Emacs development takes place on emacs-devel@gnu.org.
You can subscribe to the mailing lists, or see the list archives,
by following links from http://savannah.gnu.org/mail/?group=emacs .
+To email a patch you can use a shell command like 'git format-patch -1'
+to create a file, and then attach the file to your email. This nicely
+packages the patch's commit message and changes. To send just one
+such patch without additional remarks, you can use a command like
+'git send-email --to=bug-gnu-emacs@gnu.org 0001-DESCRIPTION.patch'.
+
+** Issue tracker (a.k.a. "bug tracker")
+
+The Emacs issue tracker is at http://debbugs.gnu.org/. The form
+presented by that page allows to view bug reports and search the
+database for bugs matching several criteria. Messages posted to the
+bug-gnu-emacs@gnu.org mailing list, mentioned above, are recorded by
+the tracker with the corresponding bugs/issues.
+
+GNU ELPA has a 'debbugs' package that allows accessing the tracker
+database from Emacs.
+
+Bugs needs regular attention. A large backlog of bugs is
+disheartening to the developers, and a culture of ignoring bugs is
+harmful to users, who expect software that works. Bugs have to be
+regularly looked at and acted upon. Not all bugs are critical, but at
+the least, each bug needs to be regularly re-reviewed to make sure it
+is still reproducible.
+
+The process of going through old or new bugs and acting on them is
+called bug triage. This process is described in the file
+admin/notes/triage.
+
** Document your changes.
Any change that matters to end-users should have an entry in etc/NEWS.
Think about whether your change requires updating the manuals. If you
know it does not, mark the NEWS entry with "---". If you know
that *all* the necessary documentation updates have been made, mark
-the entry with "+++". Otherwise do not mark it.
+the entry with "+++". Otherwise do not mark it.
+
+Please see (info "(elisp)Documentation Tips") or
+https://www.gnu.org/software/emacs/manual/html_node/elisp/Documentation-Tips.html
+for more specific tips on Emacs's doc style. Use 'checkdoc' to check
+for documentation errors before submitting a patch.
+
+** Test your changes.
+
+Please test your changes before committing them or sending them to the
+list. If possible, add a new test along with any bug fix or new
+functionality you commit (of course, some changes cannot be easily
+tested).
+
+Emacs uses ERT, Emacs Lisp Regression Testing, for testing. See (info
+"(ert)") or https://www.gnu.org/software/emacs/manual/html_node/ert/
+for more information on writing and running tests.
+
+To run tests on the entire Emacs tree, run "make check" from the
+top-level directory. Most tests are in the directory
+"test/". From the "test/" directory, run "make
+<filename>" to run the tests for <filename>.el(c). See
+"test/Makefile" for more information.
** Understanding Emacs Internals.
The best way to understand Emacs Internals is to read the code,
but the nodes "Tips" and "GNU Emacs Internals" in the Appendix
-of the Emacs Lisp Reference Manual may also help.
+of the Emacs Lisp Reference Manual may also help. Some source files,
+such as xdisp.c, have large commentaries describing the design and
+implementation in more detail.
The file etc/DEBUG describes how to debug Emacs bugs.
+*** Non-ASCII characters in Emacs files
+
+If you introduce non-ASCII characters into Emacs source files, it is a
+good idea to add a 'coding' cookie to the file to state its encoding.
+Please use the UTF-8 encoding unless it cannot do the job for some
+good reason. As of Emacs 24.4, it is no longer necessary to have
+explicit 'coding' cookies in *.el files if they are encoded in UTF-8,
+but other files need them even if encoded in UTF-8. However, if
+an *.el file is intended for use with older Emacs versions (e.g. if
+it's also distributed via ELPA), having an explicit encoding
+specification is still a good idea.
+
+*** Useful files in the admin/ directory
+
+See all the files in admin/notes/* . In particular, see
+admin/notes/newfile, see admin/notes/repo.
+
+The file admin/MAINTAINERS records the areas of interest of frequent
+Emacs contributors. If you are making changes in one of the files
+mentioned there, it is a good idea to consult the person who expressed
+an interest in that file, and/or get his/her feedback for the changes.
+If you are a frequent contributor and have interest in maintaining
+specific files, please record those interests in that file, so that
+others could be aware of that.
+
+*** git vs rename
+
+Git does not explicitly represent a file renaming; it uses a percent
+changed heuristic to deduce that a file was renamed. So if you are
+planning to make extensive changes to a file after renaming it (or
+moving it to another directory), you should:
+
+- create a feature branch
+
+- commit the rename without any changes
+
+- make other changes
+
+- merge the feature branch to trunk, _not_ squashing the commits into
+ one. The commit message on this merge should summarize the renames
+ and all the changes.
+
\f
This file is part of GNU Emacs.