Fix usage description of clang-format-diff.py.

git-svn-id: svn://svn.chromium.org/llvm-project/cfe/trunk/tools/clang-format@197668 0b72dbe1-c17f-4bc7-b9db-2b4152be0356
diff --git a/clang-format-diff.py b/clang-format-diff.py
index fee16d0..d575a8a 100755
--- a/clang-format-diff.py
+++ b/clang-format-diff.py
@@ -45,11 +45,11 @@
                       help='strip the smallest prefix containing P slashes')
   parser.add_argument('-regex', metavar='PATTERN', default=None,
                       help='custom pattern selecting file paths to reformat '
-                      '(case sensitive, override -iregex)')
+                      '(case sensitive, overrides -iregex)')
   parser.add_argument('-iregex', metavar='PATTERN', default=
                       r'.*\.(cpp|cc|c\+\+|cxx|c|cl|h|hpp|m|mm|inc|js)',
                       help='custom pattern selecting file paths to reformat '
-                      '(case insensitive, override -regex)')
+                      '(case insensitive, overridden by -regex)')
   parser.add_argument(
       '-style',
       help=