This is helpful when examining branches with disjoint roots, for example
because one is periodically merged into a subtree of the other.
With the --merge-child option, "git merge-base" will print a
first-parent ancestor of the first revision given, where the commit
printed is either a merge-base of the supplied revisions or a merge for
which one of its parents (not the first) is a merge-base.
For example, given the history:
A---C---G
\
B-----D---F
\
E
we have:
$ git merge-base F E
B
$ git merge-base --merge-child F E
D
$ git merge-base F G
C
$ git merge-base --merge-child F G
C
$ git log --left-right F...E
< F
< D
< C
< A
> E
$ git log --left-right F...E --not $(git merge-base --merge-child F E)
< F
> E
The git-log case is useful because it allows us to limit the range of
commits that we are examining for patch-identical changes when using
--cherry. For example with git-gui in git.git I know that anything
before the last merge of git-gui is not interesting:
$ time git log --cherry master...git-gui/master >/dev/null
real 0m32.731s
user 0m31.956s
sys 0m0.664s
$ time git log --cherry master...git-gui/master --not \
$(git merge-base --merge-child master git-gui/master) \
>/dev/null
real 0m2.296s
user 0m2.193s
sys 0m0.092s
The first commit is a small prerequisite to extract a useful function
from builtin/tag.c to commit.c. The second is the main change (the
commit message is identical to the text before this paragraph).
I'm not convinced that '--merge-child' is the right name for this but I
think the functionality itself is useful.
John Keeping (2):
commit: add commit_list_contains function
merge-base: add --merge-child option
Documentation/git-merge-base.txt | 6 ++++
builtin/merge-base.c | 61 ++++++++++++++++++++++++++++++++++++++--
builtin/tag.c | 10 +------
commit.c | 8 ++++++
commit.h | 1 +
t/t6010-merge-base.sh | 25 ++++++++++++++--
6 files changed, 98 insertions(+), 13 deletions(-)
--
1.8.3.rc1.289.gcb3647f
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