admin/notes/bzr

   1 NOTES ON COMMITTING TO EMACS'S BAZAAR REPO    -*- outline -*-
   2
   3 * Install changes only on one branch, let them get merged elsewhere if needed.
   4 In particular, install bug-fixes only on the release branch (if there
   5 is one) and let them get synced to the trunk; do not install them by
   6 hand on the trunk as well.  E.g. if there is an active "emacs-23" branch
   7 and you have a bug-fix appropriate for the next Emacs-23.x release,
   8 install it only on the emacs-23 branch, not on the trunk as well.
   9
  10 Installing things manually into more than one branch makes merges more
  11 difficult.
  12
  13 http://lists.gnu.org/archive/html/emacs-devel/2010-03/msg01124.html
  14
  15 * Backporting a bug-fix from the trunk to a branch (e.g. "emacs-23").
  16 Label the commit as a backport, e.g. by starting the commit message with
  17 "Backport:".  This is helpful for the person merging the release branch
  18 to the trunk.
  19
  20 http://lists.gnu.org/archive/html/emacs-devel/2010-05/msg00262.html
  21
  22 * Installing changes from your personal branches.
  23 If your branch has only a single commit, or many different real
  24 commits, it is fine to do a merge.  If your branch has only a very
  25 small number of "real" commits, but several "merge from trunks", it is
  26 preferred that you take your branch's diff, apply it to the trunk, and
  27 commit directly, not merge.  This keeps the history cleaner.
  28
  29 In general, when working on some feature in a separate branch, it is
  30 preferable not to merge from trunk until you are done with the
  31 feature.  Unless you really need some change that was done on the
  32 trunk while you were developing on the branch, you don't really need
  33 those merges; just merge once, when you are done with the feature, and
  34 Bazaar will take care of the rest.  Bazaar is much better in this than
  35 CVS, so interim merges are unnecessary.
  36
  37 Or use shelves; or rebase; or do something else.  See the thread for
  38 yet another fun excursion into the exciting world of version control.
  39
  40 http://lists.gnu.org/archive/html/emacs-devel/2010-04/msg00086.html
  41
  42 * Installing changes from gnulib
  43 Some of the files in Emacs are copied from gnulib.  To synchronize
  44 these files from the version of gnulib that you have checked out into
  45 a sibling directory of your branch, type "make sync-from-gnulib"; this
  46 will check out the latest version of gnulib if there is no sibling
  47 directory already.  It is a good idea to run "bzr status" afterwards,
  48 so that if a gnulib module added a file, you can record the new file
  49 using "bzr add".  After synchronizing from gnulib, do a "make" in the
  50 usual way.
  51
  52 To change the set of gnulib modules, change the GNULIB_MODULES
  53 variable in the top-level Makefile.in, and then run:
  54
  55   ./config.status
  56   make sync-from-gnulib
  57   bzr status
  58
  59 The last command will mention files that may need to be added using
  60 "bzr add".  If you remove a gnulib module, or if a gnulib module
  61 removes a file, then remove the corresponding files by hand.
  62
  63 * How to merge changes from emacs-23 to trunk
  64
  65 The following description uses bound branches, presumably it works in
  66 a similar way with unbound ones.
  67
  68 0) (First time only) Get the bzr changelog_merge plugin:
  69
  70 cd ~/.bazaar/plugins
  71 bzr branch lp:bzr-changelog-merge
  72 mv bzr-changelog-merge changelog_merge
  73
  74 This will make merging ChangeLogs a lot smoother.  It merges new
  75 entries to the top of the file, rather than trying to fit them in
  76 mid-way through.
  77
  78 Sigh.  This plugin has a drawback.  People often like to edit older
  79 ChangeLog entries, not at the head of the file.  Frequently they do
  80 this in the same commit as making new entries.  Using this plugin
  81 will merge ALL changed entries (including older ones) to the top of
  82 the destination file.
  83
  84 1) Get clean, up-to-date copies of the emacs-23 and trunk branches.
  85 Check for any uncommitted changes with bzr status.
  86
  87 2) M-x cd /path/to/trunk
  88
  89 The first time only, do this:
  90 cd .bzr/branch
  91 Add the following line to branch.conf:
  92 changelog_merge_files = ChangeLog
  93
  94 3) load admin/bzrmerge.el
  95
  96 4) M-x bzrmerge RET /path/to/emacs-23 RET
  97
  98 It will prompt about revisions that should be skipped, based on the
  99 regexp in bzrmerge-missing.  If there are more revisions that you know
 100 need skipping, you'll have to do that by hand.
 101
 102 5) It will stop if there are any conflicts.  Resolve them.
 103 Using smerge-mode, there are menu items to skip to the next conflict,
 104 and to take either the trunk, branch, or both copies.
 105
 106 6) After resolving all conflicts, you might need to run the bzmerge
 107 command again if there are more revisions still to merge.
 108
 109 Do not commit (or exit Emacs) until you have run bzrmerge to completion.
 110
 111 Before committing, check bzr status and bzr diff output.
 112 If you have run bzrmerge enough times, the "pending merge tip" in bzr
 113 status should be the last revision from the emacs-23 branch, and
 114 bzr status -v should show all the revisions you expect to merge.
 115
 116 (Note that it will also show "skipped" revisions.  This is expected,
 117 and is due to a technical limitation of bzr.  The log data for those
 118 revisions gets merged, the actual changes themselves do not.
 119 http://lists.gnu.org/archive/html/emacs-devel/2011-01/msg00609.html )
 120
 121 In particular, check the ChangeLog entries (eg in case too many
 122 entries have been included or whitespace between entries needs fixing).
 123 bzrmerge tries to fix up the dates to today's date, but it only does
 124 this where there are conflicts.  If you used the changelog_merge plugin,
 125 there won't be any conflicts, and (at time of writing) you will need
 126 to adjust dates by hand.  In any case, if someone made multiple
 127 ChangeLog entries on different days in the branch, you may wish to
 128 collapse them all to a single entry for that author in the trunk
 129 (because in the trunk they all appear under the same date).
 130 Obviously, if there are multiple changes to the same file by different
 131 authors, don't break the logical ordering in doing this.
 132
 133 Notes:
 134
 135 1) A lot that was in tramp.el in emacs-23 has moved to tramp-sh.el in
 136 the trunk.  If you end up with a conflict in tramp.el, the changes may
 137 need to go to tramp-sh.el instead.  Remember to update the file name in
 138 the ChangeLog.
 139
 140 2) If a file is modified in emacs-23, and deleted in the trunk, you
 141 get a "contents conflict".  Assuming the changes don't need to be in
 142 the trunk at all, use `bzr resolve path/to/file --take-this' to keep the
 143 trunk version.  Prior to bzr 2.2.3, this may fail.  You can just
 144 delete the .OTHER etc files by hand and use bzr resolve path/to/file.
 145
 146 3) Conflicts in autoload md5sums in comments.  Strictly speaking, the
 147 right thing to do is merge everything else, resolve the conflict by
 148 choosing either the trunk or branch version, then run `make -C lisp
 149 autoloads' to update the md5sums to the correct trunk value before
 150 committing.
 151
 152 * Re-adding a file that has been removed from the repository
 153
 154 It's easy to get this wrong. Let's suppose you've done:
 155
 156 bzr remove file; bzr commit
 157
 158 and now, sometime later, you realize this was a mistake and file needs
 159 to be brought back.  DON'T just do:
 160
 161 bzr add file; bzr commit
 162
 163 This restores file, but without its history (`bzr log file' will be
 164 very short).  This is because file gets re-added with a new file-id
 165 (use `bzr file-id file' to see the id).
 166
 167 Insteading of adding the file, try:
 168
 169 bzr revert -rN file; bzr commit
 170
 171 where revision N+1 is the one where file was removed.
 172
 173 You could also try `bzr add --file-ids-from', if you have a copy of
 174 another branch where file still exists.