diff options
| -rw-r--r-- | Documentation/git-merge-base.txt | 28 | ||||
| -rw-r--r-- | builtin/merge-base.c | 22 |
2 files changed, 50 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], diff --git a/builtin/merge-base.c b/builtin/merge-base.c index 4f30f1b0c8..0568b07e1d 100644 --- a/builtin/merge-base.c +++ b/builtin/merge-base.c @@ -26,6 +26,7 @@ static const char * const merge_base_usage[] = { "git merge-base [-a|--all] <commit> <commit>...", "git merge-base [-a|--all] --octopus <commit>...", "git merge-base --independent <commit>...", + "git merge-base --is-ancestor <commit> <commit>", NULL }; @@ -70,6 +71,20 @@ static int handle_octopus(int count, const char **args, int reduce, int show_all return 0; } +static int handle_is_ancestor(int argc, const char **argv) +{ + struct commit *one, *two; + + if (argc != 2) + die("--is-ancestor takes exactly two commits"); + one = get_commit_reference(argv[0]); + two = get_commit_reference(argv[1]); + if (in_merge_bases(one, two)) + return 0; + else + return 1; +} + int cmd_merge_base(int argc, const char **argv, const char *prefix) { struct commit **rev; @@ -77,11 +92,14 @@ int cmd_merge_base(int argc, const char **argv, const char *prefix) int show_all = 0; int octopus = 0; int reduce = 0; + int is_ancestor = 0; struct option options[] = { OPT_BOOLEAN('a', "all", &show_all, "output all common ancestors"), OPT_BOOLEAN(0, "octopus", &octopus, "find ancestors for a single n-way merge"), OPT_BOOLEAN(0, "independent", &reduce, "list revs not reachable from others"), + OPT_BOOLEAN(0, "is-ancestor", &is_ancestor, + "is the first one ancestor of the other?"), OPT_END() }; @@ -89,6 +107,10 @@ int cmd_merge_base(int argc, const char **argv, const char *prefix) argc = parse_options(argc, argv, prefix, options, merge_base_usage, 0); if (!octopus && !reduce && argc < 2) usage_with_options(merge_base_usage, options); + if (is_ancestor && (show_all | octopus | reduce)) + die("--is-ancestor cannot be used with other options"); + if (is_ancestor) + return handle_is_ancestor(argc, argv); if (reduce && (show_all || octopus)) die("--independent cannot be used with other options"); |