повторное использование записанного разрешения конфликтующих слияний (Reuse recorded resolution of conflicted merges)
Имя (Name)
git-rerere - Reuse recorded resolution of conflicted merges
Синопсис (Synopsis)
git rerere [clear|forget <pathspec>|diff|remaining|status|gc]
Описание (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.
Команды (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.
Обсуждение (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.
