NOTES ON COMMITTING TO EMACS'S REPOSITORY -*- outline -*- * Commit metainformation ** Commit in the author's name If installing changes written by someone else, commit them in their name, not yours. ** Commit message format Commit messages should follow the conventions used in all modern distributed version-control systems. That is, they should consist of - A self-contained topic line, preferably no more than 75 chars long. - If other content follows the topic line, there should be a blank line separating the two. - Follow the blank line with ChangeLog-like entries for the specific changes you made, if any. (As long as Emacs maintains ChangeLog files, just copy the entries you made in them to the commit message after the blank line.) - 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. (Rather than anything involving "ditto" and suchlike.) ** Unnecessary metainformation There is no need to make separate change log 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. ** Using vc-dwim to maintain commit messages You can use vc-dwim to maintain commit messages in ChangeLog format. When you create a source directory FOO, run the shell command 'cd FOO; 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 add-change-log-entry-other-window, and commit the change using the shell command 'cd FOO; vc-dwim'. Type 'vc-dwim --help' for more info. * Commit to the right branch Development normally takes places on the trunk. Sometimes specialized features are developed on separate branches before possibly being merged to the trunk. 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. No new features may be added after this point. This is usually some months before the release. Shortly before the release, a release branch is created, and the trunk is then free for development. For example, "emacs-23" for Emacs 23.2 and later, "EMACS_23_1_RC" for 23.1, "EMACS_22_BASE" for 22.x, and "EMACS_21_1_RC" for 21.x. Consult emacs-devel for exactly what kinds of changes are allowed on what branch at any time. ** elpa This branch does not contain a copy of Emacs, but of the Emacs Lisp package archive (elpa.gnu.org). See admin/notes/elpa for further explanation, and the README file in the branch for usage instructions. * Install changes only on one branch, let them get merged elsewhere if needed. In particular, install bug-fixes only on the release branch (if there is one) and let them get synced to the trunk; do not install them by hand on the trunk as well. E.g. if there is an active "emacs-24" branch and you have a bug-fix appropriate for the next emacs-24.x release, install it only on the emacs-24 branch, not on the trunk as well. Installing things manually into more than one branch makes merges more difficult. http://lists.gnu.org/archive/html/emacs-devel/2010-03/msg01124.html The exception is, if you know that the change will be difficult to merge to the trunk (eg because the trunk code has changed a lot). In that case, it's helpful if you can apply the change to both trunk and branch yourself (when committing the branch change, indicate in the commit log that it should not be merged to the trunk; see below). * Installing changes from your personal branches. If your branch has only a single commit, or many different real commits, it is fine to do a merge. If your branch has only a very small number of "real" commits, but several "merge from trunks", it is preferred that you take your branch's diff, apply it to the trunk, and commit directly, not merge. This keeps the history cleaner. In general, when working on some feature in a separate branch, it is preferable not to merge from trunk until you are done with the feature. Unless you really need some change that was done on the trunk while you were developing on the branch, you don't really need those merges; just merge once, when you are done with the feature, and Bazaar will take care of the rest. Bazaar is much better in this than CVS, so interim merges are unnecessary. Or use shelves; or rebase; or do something else. See the thread for yet another fun excursion into the exciting world of version control. http://lists.gnu.org/archive/html/emacs-devel/2010-04/msg00086.html * Installing changes from gnulib Some of the files in Emacs are copied from gnulib. To synchronize these files from the version of gnulib that you have checked out into a sibling directory of your branch, type "admin/merge-gnulib"; this will check out the latest version of gnulib if there is no sibling directory already. It is a good idea to run "git status" afterwards, so that if a gnulib module added a file, you can record the new file using "git add". After synchronizing from gnulib, do a "make" in the usual way. To change the set of gnulib modules, change the GNULIB_MODULES variable in admin/merge-gnulib before running it. If you remove a gnulib module, or if a gnulib module removes a file, then remove the corresponding files by hand. * Backporting a bug-fix from the trunk to a branch (e.g. "emacs-24"). Indicate in the commit log that there is no need to merge the commit to the trunk, e.g. start the commit message with "Backport:". This is helpful for the person merging the release branch to the trunk. http://lists.gnu.org/archive/html/emacs-devel/2010-05/msg00262.html * How to merge changes from emacs-24 to trunk [The section on git merge procedure has not yet been written. Among other things, the ChangeLog file is now automatically generated.] Inspect the change log entries (e.g. in case too many entries have been included or whitespace between entries needs fixing). If someone made multiple change log entries on different days in the branch, you may wish to collapse them all to a single entry for that author in the trunk (because in the trunk they all appear under the same date). Obviously, if there are multiple changes to the same file by different authors, don't break the logical ordering in doing this. You may see conflicts in autoload md5sums in comments. Strictly speaking, the right thing to do is merge everything else, resolve the conflict by choosing either the trunk or branch version, then run `make -C lisp autoloads' to update the md5sums to the correct trunk value before committing. * Re-adding a file that has been removed from the repository Let's suppose you've done: git rm file; git commit -a You can just restore a copy of the file and then re-add it; git does not have per-file history so this will not harm anything. Alternatively, you can do git revert XXXXX where XXXXX is the hash of the commit in which file was removed. This backs out the entire changeset the deletion was part of, which is often more appropriate. * Undoing a commit (uncommitting) If you have not pushed the commit, you may be able to use `git reset --hard' with a hash argument to revert the your local repo copy to the pre-commit state. If you have pushed commit, resetting will be ineffective because it will only vanish the commit in your local copy. Instead, use `git revert', giving it the commit ID as argument. This will create a new commit that backs out the change. Then push that. Note that git will generate a log message for the revert that includes a git hash. Please edit this to refer to the commit by the first line of its log comment, or by committer and date, or by something else that is not the hash. As noted previously, it is best to avoid hashes in comments in case we someday have to change version-control systems again. * Bisecting This is a semi-automated way to find the revision that introduced a bug. Browse `git help bisect' for technical instructions.