Using Git Rerere for Conflict Resolution

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 linkgit:gitattributes[5] can be used. GIT --- Part of the linkgit:git[1] suite

Git Rerere is a feature that helps resolve conflicts in merges by reusing previously recorded resolutions, making it easier to manage conflicts when working with topic branches and rebasing, and it can be used automatically by git merge and git rebase with the rerere.enabled config variable enabled.