'Implement source.get_new_files by using rsync listing feature.'

def get_new_files(self):

    files = {}
    for (src, prefix) in self.sources:
        output = utils.system_output((self._cmd_template % (self.exclude, self.prefix, src)))
        files.update(self._parse_output(output, prefix))
    return self._get_new_files(files)
