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97 lines
2.7 KiB
97 lines
2.7 KiB
git-merge-base(1) |
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================= |
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NAME |
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---- |
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git-merge-base - Find as good common ancestors as possible for a merge |
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SYNOPSIS |
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-------- |
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'git merge-base' [--all] <commit> <commit>... |
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DESCRIPTION |
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----------- |
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'git-merge-base' finds best common ancestor(s) between two commits to use |
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in a three-way merge. One common ancestor is 'better' than another common |
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ancestor if the latter is an ancestor of the former. A common ancestor |
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that does not have any better common ancestor than it is a 'best common |
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ancestor', i.e. a 'merge base'. Note that there can be more than one |
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merge bases between two commits. |
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Among the two commits to compute their merge bases, one is specified by |
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the first commit argument on the command line; the other commit is a |
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(possibly hypothetical) commit that is a merge across all the remaining |
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commits on the command line. As the most common special case, giving only |
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two commits from the command line means computing the merge base between |
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the given two commits. |
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OPTIONS |
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------- |
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--all:: |
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Output all merge bases for the commits, instead of just one. |
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DISCUSSION |
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---------- |
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Given two commits 'A' and 'B', `git merge-base A B` will output a commit |
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which is reachable from both 'A' and 'B' through the parent relationship. |
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For example, with this topology: |
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o---o---o---B |
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/ |
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---o---1---o---o---o---A |
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the merge base between 'A' and 'B' is '1'. |
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Given three commits 'A', 'B' and 'C', `git merge-base A B C` will compute the |
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merge base between 'A' and an hypothetical commit 'M', which is a merge |
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between 'B' and 'C'. For example, with this topology: |
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o---o---o---o---C |
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/ |
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/ o---o---o---B |
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/ / |
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---2---1---o---o---o---A |
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the result of `git merge-base A B C` is '1'. This is because the |
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equivalent topology with a merge commit 'M' between 'B' and 'C' is: |
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o---o---o---o---o |
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/ \ |
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/ o---o---o---o---M |
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/ / |
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---2---1---o---o---o---A |
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and the result of `git merge-base A M` is '1'. Commit '2' is also a |
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common ancestor between 'A' and 'M', but '1' is a better common ancestor, |
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because '2' is an ancestor of '1'. Hence, '2' is not a merge base. |
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When the history involves criss-cross merges, there can be more than one |
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'best' common ancestors between two commits. For example, with this |
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topology: |
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---1---o---A |
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\ / |
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X |
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/ \ |
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---2---o---o---B |
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both '1' and '2' are merge-base of A and B. Neither one is better than |
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the other (both are 'best' merge base). When `--all` option is not given, |
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it is unspecified which best one is output. |
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Author |
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------ |
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Written by Linus Torvalds <torvalds@osdl.org> |
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Documentation |
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-------------- |
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Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel.org>. |
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GIT |
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--- |
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Part of the linkgit:git[1] suite
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