1git-rerere(1) 2============= 3 4NAME 5---- 6git-rerere - Reuse recorded resolve 7 8SYNOPSIS 9-------- 10'git-rerere' [clear|diff|status] 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[NOTE] 26You need to create `$GIT_DIR/rr-cache` directory to enable this 27command. 28 29 30COMMANDS 31-------- 32 33Normally, git-rerere is run without arguments or user-intervention. 34However, it has several commands that allow it to interact with 35its working state. 36 37'clear':: 38 39This resets the metadata used by rerere if a merge resolution is to be 40is aborted. Calling gitlink:git-am[1] --skip or gitlink:git-rebase[1] 41[--skip|--abort] will automatcally invoke this command. 42 43'diff':: 44 45This displays diffs for the current state of the resolution. It is 46useful for tracking what has changed while the user is resolving 47conflicts. Additional arguments are passed directly to the system 48diff(1) command installed in PATH. 49 50'status':: 51 52Like diff, but this only prints the filenames that will be tracked 53for resolutions. 54 55'gc':: 56 57This command is used to prune records of conflicted merge that 58occurred long time ago. 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 pull . 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 pull . master 103 $ ... work on both topic and master branches 104 $ git checkout master 105 $ git pull . 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 pull . master 126 $ git reset --hard HEAD^ ;# rewind the test merge 127 $ ... work on both topic and master branches 128 $ git checkout master 129 $ git pull . 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 update-index` when you are 163satisfied. 164 165As a convenience measure, `git-merge` automatically invokes 166`git-rerere` when it exits with a failed automerge, which 167records it if it is a new conflict, or reuses the earlier hand 168resolve when it is not. `git-commit` also invokes `git-rerere` 169when recording a merge result. What this means is that you do 170not have to do anything special yourself (Note: you still have 171to create `$GIT_DIR/rr-cache` directory to enable this command). 172 173In our example, when you did the test merge, the manual 174resolution is recorded, and it will be reused when you do the 175actual merge later with updated master and topic branch, as long 176as the earlier resolution is still applicable. 177 178The information `git-rerere` records is also used when running 179`git-rebase`. After blowing away the test merge and continuing 180development on the topic branch: 181 182------------ 183 o---*---o-------o---o topic 184 / 185 o---o---o---*---o---o---o---o master 186 187 $ git rebase master topic 188 189 o---*---o-------o---o topic 190 / 191 o---o---o---*---o---o---o---o master 192------------ 193 194you could run `git rebase master topic`, to keep yourself 195up-to-date even before your topic is ready to be sent upstream. 196This would result in falling back to three-way merge, and it 197would conflict the same way the test merge you resolved earlier. 198`git-rerere` is run by `git rebase` to help you resolve this 199conflict. 200 201 202Author 203------ 204Written by Junio C Hamano <junkio@cox.net> 205 206GIT 207--- 208Part of the gitlink:git[7] suite