git-rerere

GIT-RERERE(1)                      Git Manual                      GIT-RERERE(1)



NAME
       git-rerere - Reuse recorded resolution of conflicted merges

SYNOPSIS
       git rerere [clear|forget <pathspec>|diff|remaining|status|gc]


DESCRIPTION
       In a workflow employing relatively long lived topic branches, the
       developer sometimes needs to resolve the same conflicts over and over
       again until the topic branches are done (either merged to the "release"
       branch, or sent out and accepted upstream).

       This command assists the developer in this process by recording
       conflicted automerge results and corresponding hand resolve results on
       the initial manual merge, and applying previously recorded hand
       resolutions to their corresponding automerge results.

           Note
           You need to set the configuration variable rerere.enabled in order 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
           Reset the metadata used by rerere if a merge resolution is to be
           aborted. Calling git am [--skip|--abort] or git rebase
           [--skip|--abort] will automatically invoke this command.

       forget <pathspec>
           Reset the conflict resolutions which rerere has recorded for the
           current conflict in <pathspec>.

       diff
           Display 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 command
           installed in PATH.

       status
           Print paths with conflicts whose merge resolution rerere will record.

       remaining
           Print paths with conflicts that have not been autoresolved by rerere.
           This includes paths whose resolutions cannot be tracked by rerere,
           such as conflicting submodules.

       gc
           Prune records of conflicted merges that occurred a long time ago. By
           default, unresolved conflicts older than 15 days and resolved
           conflicts older than 60 days are pruned. These defaults are
           controlled via the gc.rerereUnresolved and gc.rerereResolved
           configuration variables respectively.

DISCUSSION
       When your topic branch modifies an 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 switch 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 switch topic
                   $ git merge master
                   $ ... work on both topic and master branches
                   $ git switch 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 switch topic
                   $ git merge master
                   $ git reset --hard HEAD^ ;# rewind the test merge
                   $ ... work on both topic and master branches
                   $ git switch 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,
       this conflict is often the same conflict you resolved when you created
       the test merge you blew away. git rerere helps you resolve this final
       conflicted merge using the information from your earlier hand resolve.

       Running the 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 will record the
       resolved state of these files. Suppose you did this when you created the
       test merge of master into the topic branch.

       Next time, after seeing the same conflicted automerge, running git rerere
       will perform a three-way merge between the earlier conflicted automerge,
       the earlier manual resolution, and the current conflicted automerge. If
       this three-way merge resolves cleanly, the result is written out to your
       working tree file, so you do 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 upon
       exiting with a failed automerge and git rerere records the hand resolve
       when it is a new conflict, or reuses the earlier hand resolve when it is
       not. git commit also invokes git rerere when committing a merge result.
       What this means is that you do not have to do anything special yourself
       (besides enabling the rerere.enabled config variable).

       In our example, when you do the test merge, the manual resolution is
       recorded, and it will be reused when you do the actual merge later with
       the updated master and topic branch, as long as the recorded 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 bring yourself up to date
       before your topic is ready to be sent upstream. This would result in
       falling back to a three-way merge, and it would conflict the same way as
       the test merge you resolved earlier. git rerere will be run by git rebase
       to help you resolve this conflict.

       [NOTE] git rerere relies on the conflict markers in the file to detect
       the conflict. If the file already contains lines that look the same as
       lines with conflict markers, git rerere may fail to record a conflict
       resolution. To work around this, the conflict-marker-size setting in
       gitattributes(5) can be used.

GIT
       Part of the git(1) suite



Git 2.30.0                         12/28/2020                      GIT-RERERE(1)