make "find_ref_by_name" a public function

This was a static in remote.c, but is generally useful.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

refs.c

@@ -1445,3 +1445,11 @@ int update_ref(const char *action, const char *refname,
 	}
 	return 0;
 }
+
+struct ref *find_ref_by_name(struct ref *list, const char *name)
+{
+	for ( ; list; list = list->next)
+		if (!strcmp(list->name, name))
+			return list;
+	return NULL;
+}