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 The exception is, if you know that the change will be difficult to
  16 merge to the trunk (eg because the trunk code has changed a lot).
  17 In that case, it's helpful if you can apply the change to both trunk
  18 and branch yourself (when committing the branch change, indicate
  19 in the commit log that it should not be merged to the trunk; see below).
  20
  21 * Backporting a bug-fix from the trunk to a branch (e.g. "emacs-23").
  22 Indicate in the commit log that there is no need to merge the commit
  23 to the trunk.  Anything that matches `bzrmerge-skip-regexp' will do;
  24 eg start the commit message with "Backport:".  This is helpful for the
  25 person merging the release branch to the trunk.
  26
  27 http://lists.gnu.org/archive/html/emacs-devel/2010-05/msg00262.html
  28
  29 * Installing changes from your personal branches.
  30 If your branch has only a single commit, or many different real
  31 commits, it is fine to do a merge.  If your branch has only a very
  32 small number of "real" commits, but several "merge from trunks", it is
  33 preferred that you take your branch's diff, apply it to the trunk, and
  34 commit directly, not merge.  This keeps the history cleaner.
  35
  36 In general, when working on some feature in a separate branch, it is
  37 preferable not to merge from trunk until you are done with the
  38 feature.  Unless you really need some change that was done on the
  39 trunk while you were developing on the branch, you don't really need
  40 those merges; just merge once, when you are done with the feature, and
  41 Bazaar will take care of the rest.  Bazaar is much better in this than
  42 CVS, so interim merges are unnecessary.
  43
  44 Or use shelves; or rebase; or do something else.  See the thread for
  45 yet another fun excursion into the exciting world of version control.
  46
  47 http://lists.gnu.org/archive/html/emacs-devel/2010-04/msg00086.html
  48
  49 * Installing changes from gnulib
  50 Some of the files in Emacs are copied from gnulib.  To synchronize
  51 these files from the version of gnulib that you have checked out into
  52 a sibling directory of your branch, type "make sync-from-gnulib"; this
  53 will check out the latest version of gnulib if there is no sibling
  54 directory already.  It is a good idea to run "bzr status" afterwards,
  55 so that if a gnulib module added a file, you can record the new file
  56 using "bzr add".  After synchronizing from gnulib, do a "make" in the
  57 usual way.
  58
  59 To change the set of gnulib modules, change the GNULIB_MODULES
  60 variable in the top-level Makefile.in, and then run:
  61
  62   ./config.status
  63   make sync-from-gnulib
  64   bzr status
  65
  66 The last command will mention files that may need to be added using
  67 "bzr add".  If you remove a gnulib module, or if a gnulib module
  68 removes a file, then remove the corresponding files by hand.
  69
  70 * How to merge changes from emacs-23 to trunk
  71
  72 The following description uses bound branches, presumably it works in
  73 a similar way with unbound ones.
  74
  75 0) (First time only) Get the bzr changelog_merge plugin
  76 (this will be included by default in bzr 2.4 onwards):
  77
  78 cd ~/.bazaar/plugins
  79 bzr branch http://bazaar.launchpad.net/~spiv/bzr-changelog-merge/trunk
  80 mv trunk changelog_merge
  81
  82 This should make merging ChangeLogs smoother.  It merges new entries
  83 to the top of the file, rather than trying to fit them in mid-way
  84 through.  Newer versions of the plugin should also be able to deal
  85 with changes to *old* ChangeLog entries, that should not be floated to
  86 the head of the file (see launchpad#723968).
  87
  88 Maybe the default Emacs behavior without this plugin is better,
  89 though, it's not clear yet.
  90
  91 1) Get clean, up-to-date copies of the emacs-23 and trunk branches.
  92 Check for any uncommitted changes with bzr status.
  93
  94 2) M-x cd /path/to/trunk
  95
  96 The first time only, do this:
  97 cd .bzr/branch
  98 Add the following line to branch.conf:
  99 changelog_merge_files = ChangeLog
 100
 101 3) load admin/bzrmerge.el
 102
 103 4) M-x bzrmerge RET /path/to/emacs-23 RET
 104
 105 It will prompt about revisions that should be skipped, based on the
 106 regexp in bzrmerge-missing.  If there are more revisions that you know
 107 need skipping, you'll have to do that by hand.
 108
 109 5) It will stop if there are any conflicts.  Resolve them.
 110 Using smerge-mode, there are menu items to skip to the next conflict,
 111 and to take either the trunk, branch, or both copies.
 112
 113 6) After resolving all conflicts, you might need to run the bzmerge
 114 command again if there are more revisions still to merge.
 115
 116 Do not commit (or exit Emacs) until you have run bzrmerge to completion.
 117
 118 Before committing, check bzr status and bzr diff output.
 119 If you have run bzrmerge enough times, the "pending merge tip" in bzr
 120 status should be the last revision from the emacs-23 branch, and
 121 bzr status -v should show all the revisions you expect to merge.
 122
 123 (Note that it will also show "skipped" revisions.  This is expected,
 124 and is due to a technical limitation of bzr.  The log data for those
 125 revisions gets merged, the actual changes themselves do not.
 126 http://lists.gnu.org/archive/html/emacs-devel/2011-01/msg00609.html )
 127
 128 In particular, check the ChangeLog entries (eg in case too many
 129 entries have been included or whitespace between entries needs fixing).
 130 bzrmerge tries to fix up the dates to today's date, but it only does
 131 this where there are conflicts.  If you used the changelog_merge plugin,
 132 there won't be any conflicts, and (at time of writing) you will need
 133 to adjust dates by hand.  In any case, if someone made multiple
 134 ChangeLog entries on different days in the branch, you may wish to
 135 collapse them all to a single entry for that author in the trunk
 136 (because in the trunk they all appear under the same date).
 137 Obviously, if there are multiple changes to the same file by different
 138 authors, don't break the logical ordering in doing this.
 139
 140 Notes:
 141
 142 1) A lot that was in tramp.el in emacs-23 has moved to tramp-sh.el in
 143 the trunk.  If you end up with a conflict in tramp.el, the changes may
 144 need to go to tramp-sh.el instead.  Remember to update the file name in
 145 the ChangeLog.
 146
 147 2) If a file is modified in emacs-23, and deleted in the trunk, you
 148 get a "contents conflict".  Assuming the changes don't need to be in
 149 the trunk at all, use `bzr resolve path/to/file --take-this' to keep the
 150 trunk version.  Prior to bzr 2.2.3, this may fail.  You can just
 151 delete the .OTHER etc files by hand and use bzr resolve path/to/file.
 152
 153 3) Conflicts in autoload md5sums in comments.  Strictly speaking, the
 154 right thing to do is merge everything else, resolve the conflict by
 155 choosing either the trunk or branch version, then run `make -C lisp
 156 autoloads' to update the md5sums to the correct trunk value before
 157 committing.
 158
 159 * Re-adding a file that has been removed from the repository
 160
 161 It's easy to get this wrong. Let's suppose you've done:
 162
 163 bzr remove file; bzr commit
 164
 165 and now, sometime later, you realize this was a mistake and file needs
 166 to be brought back.  DON'T just do:
 167
 168 bzr add file; bzr commit
 169
 170 This restores file, but without its history (`bzr log file' will be
 171 very short).  This is because file gets re-added with a new file-id
 172 (use `bzr file-id file' to see the id).
 173
 174 Insteading of adding the file, try:
 175
 176 bzr revert -rN file; bzr commit
 177
 178 where revision N+1 is the one where file was removed.
 179
 180 You could also try `bzr add --file-ids-from', if you have a copy of
 181 another branch where file still exists.
 182
 183 * Loggerhead
 184
 185 Loggerhead is the bzr tool for viewing a repository over http (similar
 186 to ViewVC).  The central version is at http://bzr.savannah.gnu.org/lh/emacs,
 187 but if you just like the way this interface presents data, then if
 188 you have your own copy of the repository, you can operate your own
 189 Loggerhead server in stand-alone mode, and so help to reduce the load
 190 on Savannah:
 191
 192   bzr branch lp:loggerhead ~/.bazaar/plugins/loggerhead
 193   cd /path/to/emacs/bzr
 194   bzr serve --http
 195
 196 You may need to install some Python dependencies to get this command to work.
 197 For example, on RHEL6 I needed:
 198
 199   yum install python-paste python-simplejson
 200   yum --enablerepo=epel install python-simpletal
 201
 202 Then point your web-browser to http://127.0.0.1:8080/ .