Move patch management functions into their own file, patch.py.

patch.py

+# Copyright (c) 2010 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 re
+import subprocess2
+
+
+def auto_mangle_git_patch(patch):
+  """Mangles a patch and automatically strip out git decoration."""
+  # Git patches have a/ at the beginning of source paths.  We strip that out
+  # with a regexp rather than the -p flag to patch so we can feed either Git
+  # or svn-style patches into the same apply command.  re.sub() should be used
+  # but flags=re.MULTILINE is only in python 2.7.
+  out = []
+  for line in patch.splitlines(True):
+    # TODO: It should just process the header lines.
+    out.append(re.sub(r'^--- a/', r'--- ',
+      re.sub(r'^\+\+\+ b/', r'+++ ', line)))
+  return ''.join(out)
+
+
+def apply_patch(location, patch):
+  """Applies a svn patch, manually applying svn meta data."""
+  # TODO: Do not shell out patch to enable svn cp/mv/ren and friends
+  # TODO: Add binary support
+  # TODO: Reuse some webkit svn-apply stuff?
+  cmd = ['patch', '-p0', '--forward', '--force']
+  subprocess2.check_call(cmd, stdin=patch, cwd=location)
+