Add support for empty files, __init__.py is a common example.

tests/patch_test.py

 #!/usr/bin/env python
 # Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Unit tests for patch.py."""
 
 import logging
 import os
 import sys
@@ skipping 494 matching lines @@
     diff = (
         'diff --git a/natsort_test.py b/natsort_test.py\n'
         'new file mode 100755\n'
         '--- /dev/null\n'
         '+++ b/natsort_test.py\n'
         '@@ -0,0 +1,1 @@\n'
         '+#!/usr/bin/env python\n')
     self.assertEquals(
         [('svn:executable', '*')],
         patch.FilePatchDiff('natsort_test.py', diff, []).svn_properties)
+    diff = (
+        'diff --git a/natsort_test.py b/natsort_test.py\n'
+        'new file mode 100644\n'
+        '--- /dev/null\n'
+        '+++ b/natsort_test.py\n'
+        '@@ -0,0 +1,1 @@\n'
+        '+#!/usr/bin/env python\n')
+    self.assertEquals(
+        [], patch.FilePatchDiff('natsort_test.py', diff, []).svn_properties)
 
 
 if __name__ == '__main__':
   logging.basicConfig(level=
       [logging.WARNING, logging.INFO, logging.DEBUG][
         min(2, sys.argv.count('-v'))])
   unittest.main()