[PATCH] tags: short-circuit if no tags have ever been committed

[Bryan O'Sullivan]

# HG changeset patch
# User Bryan O'Sullivan <bryano at fb.com>
# Date 1336903312 -7200
# Node ID 652b1c4f090df25ada6b2b13f1ddc32974a605d4
# Parent  ac7012ae864dd1c37475d0fb4263b6fd7e534924
tags: short-circuit if no tags have ever been committed

diff -r ac7012ae864d -r 652b1c4f090d mercurial/tags.py
--- a/mercurial/tags.py	Sun May 13 12:01:49 2012 +0200
+++ b/mercurial/tags.py	Sun May 13 12:01:52 2012 +0200
@@ -228,6 +228,11 @@
 
     # N.B. in case 4 (nodes destroyed), "new head" really means "newly
     # exposed".
+    if not len(repo.file('.hgtags')):
+        # No tags have ever been committed, so we can avoid a
+        # potentially expensive search.
+        return (repoheads, cachefnode, None, True)
+
     newheads = [head
                 for head in repoheads
                 if head not in set(cacheheads)]