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