Command-line parsing
====================

An invalid argument causes a short error message

    >>> from findimports import main
    >>> exitcode = main(['findimports', '--nosuchargument'])
    Usage: findimports [options] [filename|dirname ...]
    <BLANKLINE>
    findimports: error: no such option: --nosuchargument

    >>> exitcode
    2

You can ask for a help message

    >>> exitcode = main(['findimports', '--help'])  # doctest: +ELLIPSIS
    Usage: findimports [options] [filename|dirname ...]
    <BLANKLINE>
    FindImports is a script that processes Python module dependencies...
    ...

The default pathname is '.'

    >>> import os
    >>> os.chdir(sample_tree)
    >>> exitcode = main(['findimports', '-pil1'])
    apple:
      os
      sys
    box:
      gc
    orange:
      gc

