48bb914ed6
The point of these sections is generally to:
1. Give credit where it is due.
2. Give the reader an idea of where to ask questions or
file bug reports.
But they don't do a good job of either case. For (1), they
are out of date and incomplete. A much more accurate answer
can be gotten through shortlog or blame. For (2), the
correct contact point is generally git@vger, and even if you
wanted to cc the contact point, the out-of-date and
incomplete fields mean you're likely sending to somebody
useless.
So let's drop the fields entirely from all manpages except
git(1) itself. We already point people to the mailing list
for bug reports there, and we can update the Authors section
to give credit to the major contributors and point to
shortlog and blame for more information.
Each page has a "This is part of git" footer, so people can
follow that to the main git manpage.
114 lines
3.4 KiB
Plaintext
114 lines
3.4 KiB
Plaintext
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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[verse]
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'git merge-base' [-a|--all] [--octopus] <commit> <commit>...
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'git merge-base' --independent <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 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 base for a pair of commits.
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Unless `--octopus` is given, among the two commits to compute the merge
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base from, one is specified by the first commit argument on the command
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line; the other commit is a (possibly hypothetical) commit that is a merge
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across all the remaining commits on the command line. As the most common
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special case, specifying only two commits on the command line means
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computing the merge base between the given two commits.
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As a consequence, the 'merge base' is not necessarily contained in each of the
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commit arguments if more than two commits are specified. This is different
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from linkgit:git-show-branch[1] when used with the `--merge-base` option.
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OPTIONS
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-------
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-a::
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--all::
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Output all merge bases for the commits, instead of just one.
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--octopus::
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Compute the best common ancestors of all supplied commits,
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in preparation for an n-way merge. This mimics the behavior
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of 'git show-branch --merge-base'.
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--independent::
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Instead of printing merge bases, print a minimal subset of
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the supplied commits with the same ancestors. In other words,
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among the commits given, list those which cannot be reached
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from any other. This mimics the behavior of 'git show-branch
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--independent'.
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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 a 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 ancestor for two commits. For example, with this 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-bases of A and B. Neither one is better than
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the other (both are 'best' merge bases). When the `--all` option is not given,
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it is unspecified which best one is output.
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See also
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--------
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linkgit:git-rev-list[1],
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linkgit:git-show-branch[1],
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linkgit:git-merge[1]
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GIT
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---
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Part of the linkgit:git[1] suite
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