[PATCH 2 of 3] ignore: only read an ignore file once

[Bryan O'Sullivan]

# HG changeset patch
# User Bryan O'Sullivan <bryano at fb.com>
# Date 1355788364 28800
# Node ID 588d2a23ca25b43dd4afd1a194343635a1255992
# Parent  c0143219521a427970cc224f0c4ea3ac7428236f
ignore: only read an ignore file once

diff --git a/mercurial/ignore.py b/mercurial/ignore.py
--- a/mercurial/ignore.py
+++ b/mercurial/ignore.py
@@ -57,6 +57,8 @@
 
     pats = {}
     for f in files:
+        if f in pats:
+            continue
         try:
             pats[f] = []
             fp = open(f)