Explicitly pass "--diff-cmd diff" to "svn diff", for users who have set some other diff tool.

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 785 matching lines @@
           SVN.CaptureLocalInfo([filename], cwd),
           bogus_dir,
           full_move,
           revision)
     finally:
       gclient_utils.RemoveDirectory(bogus_dir)
 
   @staticmethod
   def _DiffItemInternal(filename, cwd, info, bogus_dir, full_move, revision):
     """Grabs the diff data."""
-    command = ["diff", "--config-dir", bogus_dir, filename]
+    command = ["diff", "--diff-cmd", "diff", "--config-dir", bogus_dir,
+               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 91 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(['diff', '--diff-cmd', 'diff', '-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)
@@ skipping 167 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