Improve patch handling and tests.

patch.py

 # coding=utf8
 # 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.
 """Utility functions to handle patches."""
 
 import posixpath
 import os
 import re
 
@@ skipping 228 matching lines @@
 
     A svn diff can contain only property changes, in that case there will be no
     proper header. To make things worse, this property change header is
     localized.
     """
     lines = self.diff_header.splitlines()
     while lines:
       match = re.match(r'^--- ([^\t]+).*$', lines.pop(0))
       if not match:
         continue
-      if match.group(1) not in (self.filename, '/dev/null'):
-        self._fail('Unexpected diff: %s.' % match.group(1))
+      # For copy and renames, it's possible that the -- line doesn't match +++,
+      # so don't check match.group(1) to match self.filename or '/dev/null', it
+      # can be anything else.
+      # TODO(maruel): Handle rename/copy explicitly.
+      # if match.group(1) not in (self.filename, '/dev/null'):
+      #  self.source_file = match.group(1)
+      if not lines:
+        self._fail('Nothing after header.')
       match = re.match(r'^\+\+\+ ([^\t]+).*$', lines.pop(0))
       if not match:
         self._fail('Unexpected diff: --- not following +++.')
       if match.group(1) not in (self.filename, '/dev/null'):
         self._fail('Unexpected diff: %s.' % match.group(1))
       assert not lines, '_split_header() is broken'
       break
     else:
       # Cheap check to make sure the file name is at least mentioned in the
       # 'diff' header. That the only remaining invariant.
@@ skipping 12 matching lines @@
     for patch in self.patches:
       patch.set_relpath(relpath)
 
   def __iter__(self):
     for patch in self.patches:
       yield patch
 
   @property
   def filenames(self):
     return [p.filename for p in self.patches]