Teach git-describe --exact-match to avoid expensive tag searches

diff --git a/builtin-describe.c b/builtin-describe.c
index 9c958bd84b839cb501c977ecb7a23ce5400c3f2c..05e309f5ad15f9a6f85df34322bb59152b4e37be 100644 (file)
--- a/builtin-describe.c
+++ b/builtin-describe.c
@@ -174,6 +174,8 @@ static void describe(const char *arg, int last_one)
                return;
        }
 
+       if (!max_candidates)
+               die("no tag exactly matches '%s'", sha1_to_hex(cmit->object.sha1));
        if (debug)
                fprintf(stderr, "searching to describe %s\n", arg);
 
@@ -270,6 +272,8 @@ int cmd_describe(int argc, const char **argv, const char *prefix)
                OPT_BOOLEAN(0, "all",        &all, "use any ref in .git/refs"),
                OPT_BOOLEAN(0, "tags",       &tags, "use any tag in .git/refs/tags"),
                OPT__ABBREV(&abbrev),
+               OPT_SET_INT(0, "exact-match", &max_candidates,
+                           "only output exact matches", 0),
                OPT_INTEGER(0, "candidates", &max_candidates,
                            "consider <n> most recent tags (default: 10)"),
                OPT_STRING(0, "match",       &pattern, "pattern",
@@ -278,8 +282,8 @@ int cmd_describe(int argc, const char **argv, const char *prefix)
        };
 
        argc = parse_options(argc, argv, options, describe_usage, 0);
-       if (max_candidates < 1)
-               max_candidates = 1;
+       if (max_candidates < 0)
+               max_candidates = 0;
        else if (max_candidates > MAX_TAGS)
                max_candidates = MAX_TAGS;