SYNOPSIS
--------
-'git merge-base' [--all] <commit> <commit>...
+'git merge-base' [-a|--all] <commit> <commit>...
DESCRIPTION
-----------
-'git-merge-base' finds best common ancestor(s) between two commits to use
+'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 than it is a 'best common
+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 bases between two commits.
+merge base for a pair of commits.
-Among the two commits to compute their merge bases, one is specified by
+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 the most common special case, giving only
-two commits from the command line means computing the merge base between
+commits on the command line. As the most common special case, specifying only
+two commits on the command line means computing the merge base between
the given two commits.
+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 linkgit:git-show-branch[1] when used with the `--merge-base` option.
+
OPTIONS
-------
+-a::
--all::
Output all merge bases for the commits, instead of just one.
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 an hypothetical commit 'M', which is a merge
+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
because '2' is an ancestor of '1'. Hence, '2' is not a merge base.
When the history involves criss-cross merges, there can be more than one
-'best' common ancestors between two commits. For example, with this
-topology:
+'best' common ancestor for two commits. For example, with this topology:
---1---o---A
\ /
/ \
---2---o---o---B
-both '1' and '2' are merge-base of A and B. Neither one is better than
-the other (both are 'best' merge base). When `--all` option is not given,
+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.
Author