Merge branch 'mh/ref-races-optim-invalidate-cached'

* mh/ref-races-optim-invalidate-cached:
  refs: do not invalidate the packed-refs cache unnecessarily

refs.c

@@ -2174,11 +2174,14 @@ int lock_packed_refs(int flags)
 {
 	struct packed_ref_cache *packed_ref_cache;
 
-	/* Discard the old cache because it might be invalid: */
-	clear_packed_ref_cache(&ref_cache);
 	if (hold_lock_file_for_update(&packlock, git_path("packed-refs"), flags) < 0)
 		return -1;
-	/* Read the current packed-refs while holding the lock: */
+	/*
+	 * Get the current packed-refs while holding the lock.  If the
+	 * packed-refs file has been modified since we last read it,
+	 * this will automatically invalidate the cache and re-read
+	 * the packed-refs file.
+	 */
 	packed_ref_cache = get_packed_ref_cache(&ref_cache);
 	packed_ref_cache->lock = &packlock;
 	/* Increment the reference count to prevent it from being freed: */