Documentation / git-rerere.txton commit merge-recursive --renormalize (7610fa5)
   1git-rerere(1)
   2=============
   3
   4NAME
   5----
   6git-rerere - Reuse recorded resolution of conflicted merges
   7
   8SYNOPSIS
   9--------
  10'git rerere' ['clear'|'diff'|'status'|'gc']
  11
  12DESCRIPTION
  13-----------
  14
  15In a workflow employing relatively long lived topic branches,
  16the developer sometimes needs to resolve the same conflicts over
  17and over again until the topic branches are done (either merged
  18to the "release" branch, or sent out and accepted upstream).
  19
  20This command assists the developer in this process by recording
  21conflicted automerge results and corresponding hand resolve results
  22on the initial manual merge, and applying previously recorded
  23hand resolutions to their corresponding automerge results.
  24
  25[NOTE]
  26You need to set the configuration variable rerere.enabled in order to
  27enable this command.
  28
  29
  30COMMANDS
  31--------
  32
  33Normally, 'git rerere' is run without arguments or user-intervention.
  34However, it has several commands that allow it to interact with
  35its working state.
  36
  37'clear'::
  38
  39This resets the metadata used by rerere if a merge resolution is to be
  40aborted.  Calling 'git am [--skip|--abort]' or 'git rebase [--skip|--abort]'
  41will automatically invoke this command.
  42
  43'diff'::
  44
  45This displays diffs for the current state of the resolution.  It is
  46useful for tracking what has changed while the user is resolving
  47conflicts.  Additional arguments are passed directly to the system
  48'diff' command installed in PATH.
  49
  50'status'::
  51
  52Like 'diff', but this only prints the filenames that will be tracked
  53for resolutions.
  54
  55'gc'::
  56
  57This prunes records of conflicted merges that
  58occurred a long time ago.  By default, unresolved conflicts older
  59than 15 days and resolved conflicts older than 60
  60days are pruned.  These defaults are controlled via the
  61`gc.rerereunresolved` and `gc.rerereresolved` configuration
  62variables respectively.
  63
  64
  65DISCUSSION
  66----------
  67
  68When your topic branch modifies an overlapping area that your
  69master branch (or upstream) touched since your topic branch
  70forked from it, you may want to test it with the latest master,
  71even before your topic branch is ready to be pushed upstream:
  72
  73------------
  74              o---*---o topic
  75             /
  76    o---o---o---*---o---o master
  77------------
  78
  79For such a test, you need to merge master and topic somehow.
  80One way to do it is to pull master into the topic branch:
  81
  82------------
  83        $ git checkout topic
  84        $ git merge master
  85
  86              o---*---o---+ topic
  87             /           /
  88    o---o---o---*---o---o master
  89------------
  90
  91The commits marked with `*` touch the same area in the same
  92file; you need to resolve the conflicts when creating the commit
  93marked with `{plus}`.  Then you can test the result to make sure your
  94work-in-progress still works with what is in the latest master.
  95
  96After this test merge, there are two ways to continue your work
  97on the topic.  The easiest is to build on top of the test merge
  98commit `{plus}`, and when your work in the topic branch is finally
  99ready, pull the topic branch into master, and/or ask the
 100upstream to pull from you.  By that time, however, the master or
 101the upstream might have been advanced since the test merge `{plus}`,
 102in which case the final commit graph would look like this:
 103
 104------------
 105        $ git checkout topic
 106        $ git merge master
 107        $ ... work on both topic and master branches
 108        $ git checkout master
 109        $ git merge topic
 110
 111              o---*---o---+---o---o topic
 112             /           /         \
 113    o---o---o---*---o---o---o---o---+ master
 114------------
 115
 116When your topic branch is long-lived, however, your topic branch
 117would end up having many such "Merge from master" commits on it,
 118which would unnecessarily clutter the development history.
 119Readers of the Linux kernel mailing list may remember that Linus
 120complained about such too frequent test merges when a subsystem
 121maintainer asked to pull from a branch full of "useless merges".
 122
 123As an alternative, to keep the topic branch clean of test
 124merges, you could blow away the test merge, and keep building on
 125top of the tip before the test merge:
 126
 127------------
 128        $ git checkout topic
 129        $ git merge master
 130        $ git reset --hard HEAD^ ;# rewind the test merge
 131        $ ... work on both topic and master branches
 132        $ git checkout master
 133        $ git merge topic
 134
 135              o---*---o-------o---o topic
 136             /                     \
 137    o---o---o---*---o---o---o---o---+ master
 138------------
 139
 140This would leave only one merge commit when your topic branch is
 141finally ready and merged into the master branch.  This merge
 142would require you to resolve the conflict, introduced by the
 143commits marked with `*`.  However, this conflict is often the
 144same conflict you resolved when you created the test merge you
 145blew away.  'git rerere' helps you resolve this final
 146conflicted merge using the information from your earlier hand
 147resolve.
 148
 149Running the 'git rerere' command immediately after a conflicted
 150automerge records the conflicted working tree files, with the
 151usual conflict markers `<<<<<<<`, `=======`, and `>>>>>>>` in
 152them.  Later, after you are done resolving the conflicts,
 153running 'git rerere' again will record the resolved state of these
 154files.  Suppose you did this when you created the test merge of
 155master into the topic branch.
 156
 157Next time, after seeing the same conflicted automerge,
 158running 'git rerere' will perform a three-way merge between the
 159earlier conflicted automerge, the earlier manual resolution, and
 160the current conflicted automerge.
 161If this three-way merge resolves cleanly, the result is written
 162out to your working tree file, so you do not have to manually
 163resolve it.  Note that 'git rerere' leaves the index file alone,
 164so you still need to do the final sanity checks with `git diff`
 165(or `git diff -c`) and 'git add' when you are satisfied.
 166
 167As a convenience measure, 'git merge' automatically invokes
 168'git rerere' upon exiting with a failed automerge and 'git rerere'
 169records the hand resolve when it is a new conflict, or reuses the earlier hand
 170resolve when it is not.  'git commit' also invokes 'git rerere'
 171when committing a merge result.  What this means is that you do
 172not have to do anything special yourself (besides enabling
 173the rerere.enabled config variable).
 174
 175In our example, when you do the test merge, the manual
 176resolution is recorded, and it will be reused when you do the
 177actual merge later with the updated master and topic branch, as long
 178as the recorded resolution is still applicable.
 179
 180The information 'git rerere' records is also used when running
 181'git rebase'.  After blowing away the test merge and continuing
 182development on the topic branch:
 183
 184------------
 185              o---*---o-------o---o topic
 186             /
 187    o---o---o---*---o---o---o---o   master
 188
 189        $ git rebase master topic
 190
 191                                  o---*---o-------o---o topic
 192                                 /
 193    o---o---o---*---o---o---o---o   master
 194------------
 195
 196you could run `git rebase master topic`, to bring yourself
 197up-to-date before your topic is ready to be sent upstream.
 198This would result in falling back to a three-way merge, and it
 199would conflict the same way as the test merge you resolved earlier.
 200'git rerere' will be run by 'git rebase' to help you resolve this
 201conflict.
 202
 203
 204Author
 205------
 206Written by Junio C Hamano <gitster@pobox.com>
 207
 208GIT
 209---
 210Part of the linkgit:git[1] suite