---------------------------
- snakeoil.cli.arghparse: Add support for nargs param and accept '0' and '1'
values for the StoreBool action.
- snakeoil.cli.arghparse: Run early parse funcs registered in parent parsers.
- snakeoil.contexts: Add os_environ context manager for os.environ mangling.
- snakeoil.dist.distutils_extensions: Set commands for setuptools by default.
- snakeoil.dist.distutils_extensions: Fully install packages for pytest runs.
- snakeoil.version: Don't display missing extended version message for
releases.
- snakeoil.cli.arghparse: Add support for auto-registering existing
subcommands.