Fix R= line handling when there is no value and improve presubmit TAG line regex

presubmit_support.py

 #!/usr/bin/env python
 # 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.
 
 """Enables directory-specific presubmit checks to run at upload and/or commit.
 """
 
 __version__ = '1.6.1'
 
@@ skipping 655 matching lines @@
 
   Instance members:
     tags: Dictionnary of KEY=VALUE pairs found in the change description.
     self.KEY: equivalent to tags['KEY']
   """
 
   _AFFECTED_FILES = AffectedFile
 
   # Matches key/value (or "tag") lines in changelist descriptions.
   TAG_LINE_RE = re.compile(
-      '^\s*(?P<key>[A-Z][A-Z_0-9]*)\s*=\s*(?P<value>.*?)\s*$')
+      '^[ \t]*(?P<key>[A-Z][A-Z_0-9]*)[ \t]*=[ \t]*(?P<value>.*?)[ \t]*$')
   scm = ''
 
   def __init__(
       self, name, description, local_root, files, issue, patchset, author):
     if files is None:
       files = []
     self._name = name
     self._full_description = description
     # Convert root into an absolute path.
     self._local_root = os.path.abspath(local_root)
@@ skipping 612 matching lines @@
   except PresubmitFailure, e:
     print >> sys.stderr, e
     print >> sys.stderr, 'Maybe your depot_tools is out of date?'
     print >> sys.stderr, 'If all fails, contact maruel@'
     return 2
 
 
 if __name__ == '__main__':
   fix_encoding.fix_encoding()
   sys.exit(Main(None))