verify_lock(): on errors, let the caller unlock the lock

The caller already knows how to do it, so always do it in the same
place.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

refs.c

@@ -2232,14 +2232,12 @@ static int verify_lock(struct ref_lock *lock,
 			  lock->old_sha1, NULL)) {
 		int save_errno = errno;
 		error("Can't verify ref %s", lock->ref_name);
-		unlock_ref(lock);
 		errno = save_errno;
 		return -1;
 	}
 	if (hashcmp(lock->old_sha1, old_sha1)) {
 		error("Ref %s is at %s but expected %s", lock->ref_name,
 			sha1_to_hex(lock->old_sha1), sha1_to_hex(old_sha1));
-		unlock_ref(lock);
 		errno = EBUSY;
 		return -1;
 	}
@@ -2471,8 +2469,10 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
 			goto error_return;
 		}
 	}
-	if (old_sha1 && verify_lock(lock, old_sha1, mustexist))
-		return NULL;
+	if (old_sha1 && verify_lock(lock, old_sha1, mustexist)) {
+		last_errno = errno;
+		goto error_return;
+	}
 	return lock;
 
  error_return: