diff -r b89856abf4e2 -r ec8c73b02e2e mercurial/mdiff.py
--- a/mercurial/mdiff.py	Wed Nov 12 23:19:44 2014 -0800
+++ b/mercurial/mdiff.py	Wed Nov 12 23:25:32 2014 -0800
@@ -26,6 +26,7 @@
     git enables the git extended patch format
     nodates removes dates from diff headers
     nobinary ignores binary files
+    noprefix disables the 'a/' and 'b/' prefixes (ignored in plain mode)
     ignorews ignores all whitespace changes in the diff
     ignorewsamount ignores changes in the amount of whitespace
     ignoreblanklines ignores changes whose lines are all blank
@@ -39,6 +40,7 @@
         'git': False,
         'nodates': False,
         'nobinary': False,
+        'noprefix': False,
         'ignorews': False,
         'ignorewsamount': False,
         'ignoreblanklines': False,