docs: def options(self, parser, env):
          """Register commandline options with the given parser.
  
          Implement this method for normal options behavior with protection from
          OptionConflictErrors. If you override this method and want the default
          --with-$name option to be registered, be sure to call super().
  
          :param parser: argparse parser object
          :param env:
          """
          def get_help(plug):
              """Extract the help docstring from the given plugin."""
              import textwrap
              if plug.__class__.__doc__:
                  # doc sections are often indented; compress the spaces
                  return textwrap.dedent(plug.__class__.__doc__)
              return "(no help available)"
          for plug in self._plugins:
              env_opt = ENV_PREFIX + self.plugin_name(plug).upper()
              env_opt = env_opt.replace("-", "_")
              parser.add_argument("--with-%s" % self.plugin_name(plug),
                                  action="store_true",
                                  dest="plugin_%s" % self.plugin_name(plug),
                                  default=env.get(env_opt),
                                  help="Enable plugin %s: %s [%s]" %
                                  (plug.__class__.__name__, get_help(plug), env_opt))