diff -r d587925680d9 -r c84ef0047a94 mercurial/mdiff.py
--- a/mercurial/mdiff.py	Tue Nov 06 14:04:05 2012 -0800
+++ b/mercurial/mdiff.py	Thu Nov 15 12:16:08 2012 -0800
@@ -156,7 +156,7 @@
         parts.append(a)
     return ' '.join(parts) + '\n'
 
-def unidiff(a, ad, b, bd, fn1, fn2, r=None, opts=defaultopts):
+def unidiff(a, ad, b, bd, fn1, fn2, opts=defaultopts):
     def datetag(date, fn=None):
         if not opts.git and not opts.nodates:
             return '\t%s\n' % date
@@ -207,9 +207,6 @@
         if l[ln][-1] != '\n':
             l[ln] += "\n\ No newline at end of file\n"
 
-    if r:
-        l.insert(0, diffline(r, fn1, fn2, opts))
-
     return "".join(l)
 
 # creates a headerless unified diff