refname_is_safe(): use skip_prefix()

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>

refs.c

@@ -120,17 +120,19 @@ int check_refname_format(const char *refname, int flags)
 
 int refname_is_safe(const char *refname)
 {
-	if (starts_with(refname, "refs/")) {
+	const char *rest;
+
+	if (skip_prefix(refname, "refs/", &rest)) {
 		char *buf;
 		int result;
 
-		buf = xmallocz(strlen(refname));
 		/*
 		 * Does the refname try to escape refs/?
 		 * For example: refs/foo/../bar is safe but refs/foo/../../bar
 		 * is not.
 		 */
-		result = !normalize_path_copy(buf, refname + strlen("refs/"));
+		buf = xmallocz(strlen(rest));
+		result = !normalize_path_copy(buf, rest);
 		free(buf);
 		return result;
 	}