diff -r 9155257e6330 -r e57e2da803aa contrib/check-code.py
--- a/contrib/check-code.py	Fri Feb 14 00:34:20 2014 +0100
+++ b/contrib/check-code.py	Wed Feb 19 13:46:49 2014 -0800
@@ -121,6 +121,7 @@
     (r'^( *)\t', "don't use tabs to indent"),
     (r'sed (-e )?\'(\d+|/[^/]*/)i(?!\\\n)',
      "put a backslash-escaped newline after sed 'i' command"),
+    (r'^diff *-\w*u.*$\n(^  \$ |^$)', "prefix diff -u with cmp"),
   ],
   # warnings
   [