Make sure heads/foo and tags/foo do not confuse things.

When both heads/foo and tags/foo exist, get_sha1_basic("foo")
picked up the tag without complaining, which is quite confusing.
Make sure we require unambiguous form, "heads/foo" or "tags/foo"
in such cases.

Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 14 insertions, 3 deletions

diff --git a/sha1_name.c b/sha1_name.c
index be1755a70..faac158b1 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -236,6 +236,7 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 		NULL
 	};
 	const char **p;
+	int found = 0;
 
 	if (len == 40 && !get_sha1_hex(str, sha1))
 		return 0;
@@ -246,10 +247,20 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 
 	for (p = prefix; *p; p++) {
 		char *pathname = git_path("%s/%.*s", *p, len, str);
-		if (!read_ref(pathname, sha1))
-			return 0;
+		if (!read_ref(pathname, sha1)) {
+			/* Must be unique; i.e. when heads/foo and
+			 * tags/foo are both present, reject "foo".
+			 * Note that read_ref() eventually calls
+			 * get_sha1_hex() which can smudge initial
+			 * part of the buffer even if what is read
+			 * is found to be invalid halfway.
+			 */
+			if (1 < found++)
+				return -1;
+		}
 	}
-
+	if (found == 1)
+		return 0;
 	return -1;
 }