Merge branch 'sp/describe'

* sp/describe:
  Use git-describe --exact-match in bash prompt on detached HEAD
  Teach git-describe --exact-match to avoid expensive tag searches
  Avoid accessing non-tag refs in git-describe unless --all is requested
  Teach git-describe to use peeled ref information when scanning tags
  Optimize peel_ref for the current ref of a for_each_ref callback

1 files changed, 27 insertions, 8 deletions

diff --git a/builtin-describe.c b/builtin-describe.c
index 3428483134..05e309f5ad 100644
--- a/builtin-describe.c
+++ b/builtin-describe.c
@@ -46,19 +46,34 @@ static void add_to_known_names(const char *path,
 
 static int get_name(const char *path, const unsigned char *sha1, int flag, void *cb_data)
 {
-	struct commit *commit = lookup_commit_reference_gently(sha1, 1);
+	int might_be_tag = !prefixcmp(path, "refs/tags/");
+	struct commit *commit;
 	struct object *object;
-	int prio;
+	unsigned char peeled[20];
+	int is_tag, prio;
 
-	if (!commit)
+	if (!all && !might_be_tag)
 		return 0;
-	object = parse_object(sha1);
+
+	if (!peel_ref(path, peeled) && !is_null_sha1(peeled)) {
+		commit = lookup_commit_reference_gently(peeled, 1);
+		if (!commit)
+			return 0;
+		is_tag = !!hashcmp(sha1, commit->object.sha1);
+	} else {
+		commit = lookup_commit_reference_gently(sha1, 1);
+		object = parse_object(sha1);
+		if (!commit || !object)
+			return 0;
+		is_tag = object->type == OBJ_TAG;
+	}
+
 	/* If --all, then any refs are used.
 	 * If --tags, then any tags are used.
 	 * Otherwise only annotated tags are used.
 	 */
-	if (!prefixcmp(path, "refs/tags/")) {
-		if (object->type == OBJ_TAG) {
+	if (might_be_tag) {
+		if (is_tag) {
 			prio = 2;
 			if (pattern && fnmatch(pattern, path + 10, 0))
 				prio = 0;
@@ -159,6 +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);
 
@@ -255,6 +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",
@@ -263,8 +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;