Make it possible to write 'xargs'

I have this test of options parsers, and almost every one fails, including docopt: Can I write ‘xargs’?

Here’s a simplified usage string:

"""Usage:
  xargs.py [options] [COMMAND [ARG...]]

Options:
  --null,-0               Input items terminated by 0
"""

The problem is that Docopt allows interspersed options, per the GNU(?) convention. (This is a good default! I don’t dispute that.) This means that the command line xargs.py foo -0 produces this option dictionary:

{'--null': True,
 'ARG': [],
 'COMMAND': 'foo'}

instead of this one:

{'--null': False,
 'ARG': ['-0'],
 'COMMAND': 'foo'}

Obviously I could require that the user enter -- in there, but that is both obnoxious and not the typical situation for a program which runs another command passed on the command line. (E.g. time, valgrind, env, etc.)

(Incidentally, -- handling IMO doesn’t seem very good either: If I run xargs.py -- foo what I get is

{'--null': False,
 'ARG': ['foo'],
 'COMMAND': '--'}

while standard convention is that the – is basically transparent to the program’s meaning and thus it seems like it should be transparent to the program’s code, so forcing the programmer to manually shift the positional arguments down (or explicitly list a variant of the command with --) seems wrong.)

[keleshev]

I think I changed my mind and started appreciating disable_interspersed_args, so If someone does a pull-request into a new branch (is it possible in git?) or into develop, I will include it in the next version.

However, I don’t like the name, we need to come up with something else. Maybe posixly_correct similar to getopt? Or maybe something else?

[keleshev]

0.6.0 is now released with options_first argument as discussed above. Thanks a lot guys and especially @EvanED for suggestion and discussion. I could have made a big mistake with any_options. Now, I think, docopt is much better with options_first.