Prints parser's help.

        :param prog_name: vcs main script name
        :param subcommand: command name

def print_help(self, prog_name, subcommand):
        """
        Prints parser's help.

        :param prog_name: vcs main script name
        :param subcommand: command name
        """
        parser = self.get_parser(prog_name, subcommand)
        parser.print_help()