git-merge-base
(1)
Name
git-merge-base - Find as good common ancestors as possible
for a merge
Synopsis
git merge-base [-a|--all] <commit> <commit>...
git merge-base [-a|--all] --octopus <commit>...
git merge-base --independent <commit>...
Description
Git Manual GIT-MERGE-BASE(1)
NAME
git-merge-base - Find as good common ancestors as possible
for a merge
SYNOPSIS
git merge-base [-a|--all] <commit> <commit>...
git merge-base [-a|--all] --octopus <commit>...
git merge-base --independent <commit>...
DESCRIPTION
git merge-base finds best common ancestor(s) between two
commits to use in a three-way merge. One common ancestor is
better than another common ancestor if the latter is an
ancestor of the former. A common ancestor that does not have
any better common ancestor is a best common ancestor, i.e. a
merge base. Note that there can be more than one merge base
for a pair of commits.
OPERATION MODE
As the most common special case, specifying only two commits
on the command line means computing the merge base between
the given two commits.
More generally, among the two commits to compute the merge
base from, one is specified by the first commit argument on
the command line; the other commit is a (possibly
hypothetical) commit that is a merge across all the
remaining commits on the command line.
As a consequence, the merge base is not necessarily
contained in each of the commit arguments if more than two
commits are specified. This is different from git-show-
branch(1) when used with the --merge-base option.
--octopus
Compute the best common ancestors of all supplied
commits, in preparation for an n-way merge. This mimics
the behavior of git show-branch --merge-base.
--independent
Instead of printing merge bases, print a minimal subset
of the supplied commits with the same ancestors. In
other words, among the commits given, list those which
cannot be reached from any other. This mimics the
behavior of git show-branch --independent.
OPTIONS
-a, --all
Output all merge bases for the commits, instead of just
one.
Git 1.7.9.2 Last change: 02/22/2012 1
Git Manual GIT-MERGE-BASE(1)
DISCUSSION
Given two commits A and B, git merge-base A B will output a
commit which is reachable from both A and B through the
parent relationship.
For example, with this topology:
o---o---o---B
/
---o---1---o---o---o---A
the merge base between A and B is 1.
Given three commits A, B and C, git merge-base A B C will
compute the merge base between A and a hypothetical commit
M, which is a merge between B and C. For example, with this
topology:
o---o---o---o---C
/
/ o---o---o---B
/ /
---2---1---o---o---o---A
the result of git merge-base A B C is 1. This is because the
equivalent topology with a merge commit M between B and C
is:
o---o---o---o---o
/ \
/ o---o---o---o---M
/ /
---2---1---o---o---o---A
and the result of git merge-base A M is 1. Commit 2 is also
a common ancestor between A and M, but 1 is a better common
ancestor, because 2 is an ancestor of 1. Hence, 2 is not a
merge base.
The result of git merge-base --octopus A B C is 2, because 2
is the best common ancestor of all commits.
When the history involves criss-cross merges, there can be
more than one best common ancestor for two commits. For
example, with this topology:
---1---o---A
\ /
X
/ \
---2---o---o---B
Git 1.7.9.2 Last change: 02/22/2012 2
Git Manual GIT-MERGE-BASE(1)
both 1 and 2 are merge-bases of A and B. Neither one is
better than the other (both are best merge bases). When the
--all option is not given, it is unspecified which best one
is output.
ATTRIBUTES
See attributes(5) for descriptions of the following
attributes:
+---------------+--------------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+--------------------------+
|Availability | developer/versioning/git |
+---------------+--------------------------+
|Stability | Uncommitted |
+---------------+--------------------------+
SEE ALSO
git-rev-list(1), git-show-branch(1), git-merge(1)
GIT
Part of the git(1) suite
NOTES
This software was built from source available at
https://java.net/projects/solaris-userland. The original
community source was downloaded from http://git-
core.googlecode.com/files/git-1.7.9.2.tar.gz
Further information about this software can be found on the
open source community website at http://git-scm.com/.
Git 1.7.9.2 Last change: 02/22/2012 3