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* Add a ``version`` keyword for options, allowing to use ``version`` action.
* Allow an option ``add_help_cmd`` in the root of the configuration that
automatically add a ``help`` command that show the arborescence of all
commands with their descriptions.
* Allow the use of ``argparse.SUPPRESS`` with ``__SUPPRESS__`` "builtin".
* Replace the "builtins" __CHOICES__, __MATCH__ and __FILE__ in the help
message by the respectives values of those keywords.
* Add the parameter ``allow_abbrev`` in parser configuration, controlling
abbrevations behaviour (http://bugs.python.org/issue14910).