GIT-RERERE(1) Git Manual GIT-RERERE(1)NAMEgit-rerere - Reuse recorded resolution of conflicted merges
SYNOPSISgit-rerere [clear|diff|status|gc]
DESCRIPTION
In a workflow that employs relatively long lived topic branches, the
developer sometimes needs to resolve the same conflict over and over
again until the topic branches are done (either merged to the "release"
branch, or sent out and accepted upstream).
This command helps this process by recording conflicted automerge
results and corresponding hand-resolve results on the initial manual
merge, and later by noticing the same automerge results and applying
the previously recorded hand resolution.
Note
You need to set the configuration variable rerere.enabled to enable
this command.
COMMANDS
Normally, git-rerere is run without arguments or user-intervention.
However, it has several commands that allow it to interact with its
working state.
clear This resets the metadata used by rerere if a merge resolution is
to be is aborted. Calling git-am(1)--skip or git-rebase(1)
[--skip|--abort] will automatically invoke this command.
diff This displays diffs for the current state of the resolution. It
is useful for tracking what has changed while the user is
resolving conflicts. Additional arguments are passed directly to
the system diff(1) command installed in PATH.
status Like diff, but this only prints the filenames that will be
tracked for resolutions.
gc This command is used to prune records of conflicted merge that
occurred long time ago. By default, conflicts older than 15 days
that you have not recorded their resolution, and conflicts older
than 60 days, are pruned. These are controlled with
gc.rerereunresolved and gc.rerereresolved configuration
variables.
DISCUSSION
When your topic branch modifies overlapping area that your master
branch (or upstream) touched since your topic branch forked from it,
you may want to test it with the latest master, even before your topic
branch is ready to be pushed upstream:
o---*---o topic
/
o---o---o---*---o---o master
For such a test, you need to merge master and topic somehow. One way to
do it is to pull master into the topic branch:
$ git checkout topic
$ git merge master
o---*---o---+ topic
/ /
o---o---o---*---o---o master
The commits marked with * touch the same area in the same file; you
need to resolve the conflicts when creating the commit marked with +.
Then you can test the result to make sure your work-in-progress still
works with what is in the latest master.
After this test merge, there are two ways to continue your work on the
topic. The easiest is to build on top of the test merge commit , and
when your work in the topic branch is finally ready, pull the topic
branch into master, and/or ask the upstream to pull from you. By that
time, however, the master or the upstream might have been advanced
since the test merge , in which case the final commit graph would look
like this:
$ git checkout topic
$ git merge master
$ ... work on both topic and master branches
$ git checkout master
$ git merge topic
o---*---o---+---o---o topic
/ / \
o---o---o---*---o---o---o---o---+ master
When your topic branch is long-lived, however, your topic branch would
end up having many such "Merge from master" commits on it, which would
unnecessarily clutter the development history. Readers of the Linux
kernel mailing list may remember that Linus complained about such too
frequent test merges when a subsystem maintainer asked to pull from a
branch full of "useless merges".
As an alternative, to keep the topic branch clean of test merges, you
could blow away the test merge, and keep building on top of the tip
before the test merge:
$ git checkout topic
$ git merge master
$ git reset --hard HEAD^ ;# rewind the test merge
$ ... work on both topic and master branches
$ git checkout master
$ git merge topic
o---*---o-------o---o topic
/ \
o---o---o---*---o---o---o---o---+ master
This would leave only one merge commit when your topic branch is
finally ready and merged into the master branch. This merge would
require you to resolve the conflict, introduced by the commits marked
with *. However, often this conflict is the same conflict you resolved
when you created the test merge you blew away. git-rerere command helps
you to resolve this final conflicted merge using the information from
your earlier hand resolve.
Running git-rerere command immediately after a conflicted automerge
records the conflicted working tree files, with the usual conflict
markers <<<<<<<, =======, and >>>>>>> in them. Later, after you are
done resolving the conflicts, running git-rerere again records the
resolved state of these files. Suppose you did this when you created
the test merge of master into the topic branch.
Next time, running git-rerere after seeing a conflicted automerge, if
the conflict is the same as the earlier one recorded, it is noticed and
a three-way merge between the earlier conflicted automerge, the earlier
manual resolution, and the current conflicted automerge is performed by
the command. If this three-way merge resolves cleanly, the result is
written out to your working tree file, so you would not have to
manually resolve it. Note that git-rerere leaves the index file alone,
so you still need to do the final sanity checks with git diff (or git
diff -c) and git add when you are satisfied.
As a convenience measure, git-merge automatically invokes git-rerere
when it exits with a failed automerge, which records it if it is a new
conflict, or reuses the earlier hand resolve when it is not. git-commit
also invokes git-rerere when recording a merge result. What this means
is that you do not have to do anything special yourself (Note: you
still have to set the config variable rerere.enabled to enable this
command).
In our example, when you did the test merge, the manual resolution is
recorded, and it will be reused when you do the actual merge later with
updated master and topic branch, as long as the earlier resolution is
still applicable.
The information git-rerere records is also used when running
git-rebase. After blowing away the test merge and continuing
development on the topic branch:
o---*---o-------o---o topic
/
o---o---o---*---o---o---o---o master
$ git rebase master topic
o---*---o-------o---o topic
/
o---o---o---*---o---o---o---o master
you could run git rebase master topic, to keep yourself up-to-date even
before your topic is ready to be sent upstream. This would result in
falling back to three-way merge, and it would conflict the same way the
test merge you resolved earlier. git-rerere is run by git rebase to
help you resolve this conflict.
AUTHOR
Written by Junio C Hamano <junkio@cox.net>
GIT
Part of the git(7) suite
Git 1.5.5.2 10/21/2008 GIT-RERERE(1)
