1git-merge(1) 2============ 3 4NAME 5---- 6git-merge - Join two or more development histories together 7 8 9SYNOPSIS 10-------- 11[verse] 12'git-merge' [-n] [--stat] [--no-commit] [--squash] [-s <strategy>]... 13 [-m <msg>] <remote> <remote>... 14'git-merge' <msg> HEAD <remote>... 15 16DESCRIPTION 17----------- 18This is the top-level interface to the merge machinery 19which drives multiple merge strategy scripts. 20 21The second syntax (<msg> `HEAD` <remote>) is supported for 22historical reasons. Do not use it from the command line or in 23new scripts. It is the same as `git merge -m <msg> <remote>`. 24 25 26OPTIONS 27------- 28include::merge-options.txt[] 29 30-m <msg>:: 31 The commit message to be used for the merge commit (in case 32 it is created). The `git-fmt-merge-msg` script can be used 33 to give a good default for automated `git-merge` invocations. 34 35<remote>:: 36 Other branch head merged into our branch. You need at 37 least one <remote>. Specifying more than one <remote> 38 obviously means you are trying an Octopus. 39 40include::merge-strategies.txt[] 41 42 43If you tried a merge which resulted in a complex conflicts and 44would want to start over, you can recover with 45linkgit:git-reset[1]. 46 47CONFIGURATION 48------------- 49include::merge-config.txt[] 50 51branch.<name>.mergeoptions:: 52 Sets default options for merging into branch <name>. The syntax and 53 supported options are equal to that of git-merge, but option values 54 containing whitespace characters are currently not supported. 55 56HOW MERGE WORKS 57--------------- 58 59A merge is always between the current `HEAD` and one or more 60commits (usually, branch head or tag), and the index file must 61exactly match the 62tree of `HEAD` commit (i.e. the contents of the last commit) when 63it happens. In other words, `git-diff --cached HEAD` must 64report no changes. 65 66[NOTE] 67This is a bit of a lie. In certain special cases, your index is 68allowed to be different from the tree of the `HEAD` commit. The most 69notable case is when your `HEAD` commit is already ahead of what 70is being merged, in which case your index can have arbitrary 71differences from your `HEAD` commit. Also, your index entries 72may have differences from your `HEAD` commit that match 73the result of a trivial merge (e.g. you received the same patch 74from an external source to produce the same result as what you are 75merging). For example, if a path did not exist in the common 76ancestor and your head commit but exists in the tree you are 77merging into your repository, and if you already happen to have 78that path exactly in your index, the merge does not have to 79fail. 80 81Otherwise, merge will refuse to do any harm to your repository 82(that is, it may fetch the objects from remote, and it may even 83update the local branch used to keep track of the remote branch 84with `git pull remote rbranch:lbranch`, but your working tree, 85`.git/HEAD` pointer and index file are left intact). 86 87You may have local modifications in the working tree files. In 88other words, `git-diff` is allowed to report changes. 89However, the merge uses your working tree as the working area, 90and in order to prevent the merge operation from losing such 91changes, it makes sure that they do not interfere with the 92merge. Those complex tables in read-tree documentation define 93what it means for a path to "interfere with the merge". And if 94your local modifications interfere with the merge, again, it 95stops before touching anything. 96 97So in the above two "failed merge" case, you do not have to 98worry about loss of data --- you simply were not ready to do 99a merge, so no merge happened at all. You may want to finish 100whatever you were in the middle of doing, and retry the same 101pull after you are done and ready. 102 103When things cleanly merge, these things happen: 104 1051. The results are updated both in the index file and in your 106 working tree; 1072. Index file is written out as a tree; 1083. The tree gets committed; and 1094. The `HEAD` pointer gets advanced. 110 111Because of 2., we require that the original state of the index 112file to match exactly the current `HEAD` commit; otherwise we 113will write out your local changes already registered in your 114index file along with the merge result, which is not good. 115Because 1. involves only the paths different between your 116branch and the remote branch you are pulling from during the 117merge (which is typically a fraction of the whole tree), you can 118have local modifications in your working tree as long as they do 119not overlap with what the merge updates. 120 121When there are conflicts, these things happen: 122 1231. `HEAD` stays the same. 124 1252. Cleanly merged paths are updated both in the index file and 126 in your working tree. 127 1283. For conflicting paths, the index file records up to three 129 versions; stage1 stores the version from the common ancestor, 130 stage2 from `HEAD`, and stage3 from the remote branch (you 131 can inspect the stages with `git-ls-files -u`). The working 132 tree files have the result of "merge" program; i.e. 3-way 133 merge result with familiar conflict markers `<<< === >>>`. 134 1354. No other changes are done. In particular, the local 136 modifications you had before you started merge will stay the 137 same and the index entries for them stay as they were, 138 i.e. matching `HEAD`. 139 140After seeing a conflict, you can do two things: 141 142 * Decide not to merge. The only clean-up you need are to reset 143 the index file to the `HEAD` commit to reverse 2. and to clean 144 up working tree changes made by 2. and 3.; `git-reset` can 145 be used for this. 146 147 * Resolve the conflicts. `git-diff` would report only the 148 conflicting paths because of the above 2. and 3.. Edit the 149 working tree files into a desirable shape, `git-add` or `git-rm` 150 them, to make the index file contain what the merge result 151 should be, and run `git-commit` to commit the result. 152 153 154SEE ALSO 155-------- 156linkgit:git-fmt-merge-msg[1], linkgit:git-pull[1], 157linkgit:gitattributes[5] 158 159 160Author 161------ 162Written by Junio C Hamano <junkio@cox.net> 163 164 165Documentation 166-------------- 167Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>. 168 169GIT 170--- 171Part of the linkgit:git[1] suite