Improve is_delete detection.

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 251 matching lines @@
         self._fail('Unexpected git diff: %s != %s.' % (old, match.group(1)))
       if not lines or not lines[0].startswith('+++'):
         self._fail('Missing git diff output name.')
       return
 
     match = re.match(r'^\+\+\+ (.*)$', line)
     if match:
       if not last_line.startswith('---'):
         self._fail('Unexpected git diff: --- not following +++.')
       # TODO(maruel): new == self.filename.
-      if new != self.mangle(match.group(1)) and '/dev/null' != match.group(1):
-        # TODO(maruel): Can +++ be /dev/null? If so, assert self.is_delete ==
-        # True.
+      if '/dev/null' == match.group(1):
+        self.is_delete = True
+      elif new != self.mangle(match.group(1)):
         self._fail('Unexpected git diff: %s != %s.' % (new, match.group(1)))
       if lines:
         self._fail('Crap after +++')
       # We're done.
       return
 
   def _verify_svn_header(self):
     """Sanity checks the header.
 
     A svn diff can contain only property changes, in that case there will be no
@@ skipping 31 matching lines @@
       #     match.group(1) != '/dev/null'):
       #  self.source_file = match.group(1)
       if not lines or not lines[0].startswith('+++'):
         self._fail('Nothing after header.')
       return
 
     match = re.match(r'^\+\+\+ ([^\t]+).*$', line)
     if match:
       if not last_line.startswith('---'):
         self._fail('Unexpected diff: --- not following +++.')
-      if (self.mangle(match.group(1)) != self.filename and
-          match.group(1) != '/dev/null'):
-        # TODO(maruel): Can +++ be /dev/null? If so, assert self.is_delete ==
-        # True.
+      if match.group(1) == '/dev/null':
+        self.is_delete = True
+      elif self.mangle(match.group(1)) != self.filename:
         self._fail('Unexpected diff: %s.' % match.group(1))
       if lines:
         self._fail('Crap after +++')
       # We're done.
       return
 
 
 class PatchSet(object):
   """A list of FilePatch* objects."""
 
   def __init__(self, patches):
     self.patches = patches
     for p in self.patches:
       assert isinstance(p, FilePatchBase)
 
   def set_relpath(self, relpath):
     """Used to offset the patch into a subdirectory."""
     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]