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| author | Junio C Hamano <gitster@pobox.com> | 2012-08-30 14:52:20 -0700 |
|---|---|---|
| committer | Junio C Hamano <gitster@pobox.com> | 2012-08-31 11:45:33 -0700 |
| commit | 5907cda1b2e0bd7dc5c26466f60b9cbb60288cc5 (patch) | |
| tree | 37738a51fd16874f47f6b978ef37aa1a2db00751 /Documentation | |
| parent | 94f0ced0d08c8f835992b82224231b9353490e0c (diff) | |
| download | git-5907cda1b2e0bd7dc5c26466f60b9cbb60288cc5.tar.gz | |
merge-base: "--is-ancestor A B"
In many scripted Porcelain commands, we find this idiom:
if test "$(git rev-parse --verify A)" = "$(git merge-base A B)"
then
... A is an ancestor of B ...
fi
But you do not have to compute exact merge-base only to see if A is
an ancestor of B. Give them a more direct way to use the underlying
machinery.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/git-merge-base.txt | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/Documentation/git-merge-base.txt b/Documentation/git-merge-base.txt index b295bf8330..87842e33f8 100644 --- a/Documentation/git-merge-base.txt +++ b/Documentation/git-merge-base.txt @@ -11,6 +11,7 @@ SYNOPSIS [verse] 'git merge-base' [-a|--all] <commit> <commit>... 'git merge-base' [-a|--all] --octopus <commit>... +'git merge-base' --is-ancestor <commit> <commit> 'git merge-base' --independent <commit>... DESCRIPTION @@ -50,6 +51,12 @@ from linkgit:git-show-branch[1] when used with the `--merge-base` option. from any other. This mimics the behavior of 'git show-branch --independent'. +--is-ancestor:: + Check if the first <commit> is an ancestor of the second <commit>, + and exit with status 0 if true, or with status 1 if not. + Errors are signaled by a non-zero status that is not 1. + + OPTIONS ------- -a:: @@ -110,6 +117,27 @@ 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. +A common idiom to check "fast-forward-ness" between two commits A +and B is (or at least used to be) to compute the merge base between +A and B, and check if it is the same as A, in which case, A is an +ancestor of B. You will see this idiom used often in older scripts. + + A=$(git rev-parse --verify A) + if test "$A" = "$(git merge-base A B)" + then + ... A is an ancestor of B ... + fi + +In modern git, you can say this in a more direct way: + + if git merge-base --is-ancestor A B + then + ... A is an ancestor of B ... + fi + +instead. + + See also -------- linkgit:git-rev-list[1], |