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merge-base: "--is-ancestor A B"

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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>
This commit is contained in:
Junio C Hamano
2012-08-30 14:52:20 -07:00
parent 94f0ced0d0
commit 5907cda1b2
2 changed files with 50 additions and 0 deletions
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22
builtin/merge-base.c
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@ -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");