'Process a diff range line.'

def process_range(self):

    match = re.search('^@@    -((?P<old_start>[0-9]+),)?(?P<old_count>[0-9]+)    \\+((?P<new_start>[0-9]+),)?(?P<new_count>[0-9]+)    @@', self.line)
    if (not match):
        raise Exception('Unexpected    diff    range    line.')
    self.file.old.set_start(int((match.group('old_start') or 1)), int(match.group('old_count')))
    self.file.new.set_start(int((match.group('new_start') or 1)), int(match.group('new_count')))
    self.action = self.process_content
