# HG changeset patch
# User mpm@selenic.com
# Date 1116318738 28800
# Node ID b942bbe4bb84c667f34a7796415a3e439b5b4577
# Parent  401e18c95ad381fa53adeb2f598a63fd70098e54
Fix a bug in patches() if there's not text and no patch



diff --git a/mercurial/mdiff.py b/mercurial/mdiff.py
--- a/mercurial/mdiff.py
+++ b/mercurial/mdiff.py
@@ -71,6 +71,9 @@ def patches(a, bins):
     bl = len(a) + pl
     tl = bl + bl + pl # enough for the patches and two working texts
     b1, b2 = 0, bl
+
+    if not tl: return a
+
     m = mmap.mmap(devzero.fileno(), tl, mmap.MAP_PRIVATE)
 
     # load our original text