GIT-MERGE-BASE(1)                 Git Manual                 GIT-MERGE-BASE(1)

       git-merge-base - Find as good common ancestors as possible for a merge

       git merge-base [-a|--all] <commit> <commit>...

       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.

       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,
       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 git-show-branch(1) when used with the --merge-base

       -a, --all
           Output all merge bases for the commits, instead of just one.

       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:


       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---B
               /   /

       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---M
               /   /

       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.

       When the history involves criss-cross merges, there can be more than
       one best common ancestor for two commits. For example, with this

               \ /
               / \

       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.

       Written by Linus Torvalds <[1]>

       Documentation by David Greaves, Junio C Hamano and the git-list

       Part of the git(1) suite



Git 1.7.1                         03/23/2016                 GIT-MERGE-BASE(1)