Tweak GenerateDiff:

scm.py

 # Copyright (c) 2012 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.
 
 """SCM-specific utility classes."""
 
 import cStringIO
 import glob
 import logging
 import os
@@ skipping 772 matching lines @@
     assert isinstance(filenames, (list, tuple))
     root = os.path.normcase(os.path.join(cwd, ''))
     def RelativePath(path, root):
       """We must use relative paths."""
       if os.path.normcase(path).startswith(root):
         return path[len(root):]
       return path
     # If the user specified a custom diff command in their svn config file,
     # then it'll be used when we do svn diff, which we don't want to happen
     # since we want the unified diff.  Using --diff-cmd=diff doesn't always
-    # work, since they can have another diff executable in their path that
-    # gives different line endings.  So we use a bogus temp directory as the
-    # config directory, which gets around these problems.
+    # work, since e.g. Windows cmd users may not have a "diff" executable in
+    # their path at all.  So we use an empty temporary directory as the config
+    # directory, which gets around these problems.
     bogus_dir = tempfile.mkdtemp()
+    command = ['diff', '--config-dir', bogus_dir]
     try:
       # Cleanup filenames
       filenames = [RelativePath(f, root) for f in filenames]
       # Get information about the modified items (files and directories)
-      data = dict([(f, SVN.CaptureLocalInfo([f], root)) for f in filenames])
+      data = dict((f, SVN.CaptureLocalInfo([f], root)) for f in filenames)
       diffs = []
       if full_move:
         # Eliminate modified files inside moved/copied directory.
         for (filename, info) in data.iteritems():
           if SVN.IsMovedInfo(info) and info.get("Node Kind") == "directory":
             # Remove files inside the directory.
             filenames = [f for f in filenames
                          if not f.startswith(filename + os.path.sep)]
         for filename in data.keys():
           if not filename in filenames:
@@ skipping 12 matching lines @@
             src = srcurl[len(file_root)+1:]
             try:
               srcinfo = SVN.CaptureRemoteInfo(srcurl)
             except subprocess2.CalledProcessError, e:
               if not 'Not a valid URL' in e.stderr:
                 raise
               # Assume the file was deleted. No idea how to figure out at which
               # revision the file was deleted.
               srcinfo = {'Revision': rev}
             if (srcinfo.get('Revision') != rev and
-                SVN.Capture(['diff', '-r', '%d:head' % rev, srcurl], cwd)):
+                SVN.Capture(command + ['-r', '%d:head' % rev, srcurl], cwd)):
               metaheaders.append("#$ svn cp -r %d %s %s "
                                  "### WARNING: note non-trunk copy\n" %
                                  (rev, src, filename))
             else:
               metaheaders.append("#$ cp %s %s\n" % (src,
                                                     filename))
 
         if metaheaders:
           diffs.append("### BEGIN SVN COPY METADATA\n")
           diffs.extend(metaheaders)
           diffs.append("### END SVN COPY METADATA\n")
       # Now ready to do the actual diff.
-      for filename in sorted(data.iterkeys()):
+      for filename in sorted(data):
         diffs.append(SVN._DiffItemInternal(
-            filename, cwd, data[filename], bogus_dir, full_move, revision))
+            filename, cwd, data[filename], command, full_move, revision))
       # Use StringIO since it can be messy when diffing a directory move with
       # full_move=True.
       buf = cStringIO.StringIO()
       for d in filter(None, diffs):
         buf.write(d)
       result = buf.getvalue()
       buf.close()
       return result
     finally:
       gclient_utils.RemoveDirectory(bogus_dir)
 
   @staticmethod
-  def _DiffItemInternal(filename, cwd, info, bogus_dir, full_move, revision):
+  def _DiffItemInternal(filename, cwd, info, diff_command, full_move, revision):
     """Grabs the diff data."""
-    command = ["diff", "--config-dir", bogus_dir, filename]
+    command = diff_command + [filename]
     if revision:
       command.extend(['--revision', revision])
     data = None
     if SVN.IsMovedInfo(info):
       if full_move:
         if info.get("Node Kind") == "directory":
           # Things become tricky here. It's a directory copy/move. We need to
           # diff all the files inside it.
           # This will put a lot of pressure on the heap. This is why StringIO
           # is used and converted back into a string at the end. The reason to
@@ skipping 192 matching lines @@
         # revert, like for properties.
         if not os.path.isdir(cwd):
           # '.' was deleted. It's not worth continuing.
           return
         try:
           SVN.Capture(['revert', file_status[1]], cwd=cwd)
         except subprocess2.CalledProcessError:
           if not os.path.exists(file_path):
             continue
           raise