Allow metadata file to inherit values from another configuration file

packager.py

 # coding: utf-8
 
 # This file is part of the Adblock Plus build tools,
 # Copyright (C) 2006-2012 Eyeo GmbH
 #
 # Adblock Plus is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 3 as
 # published by the Free Software Foundation.
 #
 # Adblock Plus is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
 # along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
 
 # Note: These are the base functions common to all packagers, the actual
 # packagers are implemented in packagerGecko and packagerChrome.
 
 import sys, os, re, codecs, subprocess, json, zipfile, jinja2
 from StringIO import StringIO
-from ConfigParser import SafeConfigParser
+from chainedconfigparser import ChainedConfigParser
 
 import buildtools
 
 def getDefaultFileName(baseDir, metadata, version, ext):
   return os.path.join(baseDir, '%s-%s.%s' % (metadata.get('general', 'basename'), version, ext))
 
 def getMetadataPath(baseDir):
   return os.path.join(baseDir, 'metadata')
 
 def readMetadata(baseDir):
-  metadata = SafeConfigParser()
-  metadata.optionxform = str
-  file = codecs.open(getMetadataPath(baseDir), 'rb', encoding='utf-8')
-  metadata.readfp(file)
-  file.close()
-  return metadata
+  return ChainedConfigParser(getMetadataPath(baseDir))
 
 def getBuildNum(baseDir):
   try:
     (result, dummy) = subprocess.Popen(['hg', 'id', '-R', baseDir, '-n'], stdout=subprocess.PIPE).communicate()
     return re.sub(r'\D', '', result)
   except Exception:
     return '0'
 
 def getBuildVersion(baseDir, metadata, releaseBuild, buildNum=None):
   version = metadata.get('general', 'version')
@@ skipping 66 matching lines @@
       data = self[name]
       if self.process:
         data = self.process(name, data)
       zip.writestr(name, data)
     zip.close()
 
   def zipToString(self, sortKey=None):
     buffer = StringIO()
     self.zip(buffer, sortKey=sortKey)
     return buffer.getvalue()