resolve_gitlink_ref(): avoid memory allocation in many cases

If we don't have to strip trailing '/' from the submodule path, then
don't allocate and copy the submodule name.

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

refs.c

@@ -1301,19 +1301,26 @@ const char *resolve_ref_unsafe(const char *refname, int resolve_flags,
 
 int resolve_gitlink_ref(const char *path, const char *refname, unsigned char *sha1)
 {
-	int len = strlen(path);
-	struct strbuf submodule = STRBUF_INIT;
+	size_t len = strlen(path);
 	struct ref_store *refs;
 	int flags;
 
-	while (len && path[len-1] == '/')
+	while (len && path[len - 1] == '/')
 		len--;
+
 	if (!len)
 		return -1;
 
-	strbuf_add(&submodule, path, len);
-	refs = get_ref_store(submodule.buf);
-	strbuf_release(&submodule);
+	if (path[len]) {
+		/* We need to strip off one or more trailing slashes */
+		char *stripped = xmemdupz(path, len);
+
+		refs = get_ref_store(stripped);
+		free(stripped);
+	} else {
+		refs = get_ref_store(path);
+	}
+
 	if (!refs)
 		return -1;