[argparse] mutually exclusive group with 2 sets of options

[Joseph L. Casale]

> You can probably do something similar using sub commands
> (http://docs.python.org/2/library/argparse.html#sub-commands).

The problem here is that argparse does not pass the subparser into the
parsed args and shared args between subparsers need to be declared
each time. Come execution time, when you have shared args you end
up testing for various incantations of the invoked code, you're better
off omitting subparsers and performing conditional tests after parsing
for incompatible combinations.

It's a waste of typing to write out a mode followed by params to achieve
the ops goal, I've hit the same limitation. Certainly a weakness of argparse
in my opinion. It's also a tough sell to force a user to install a package just
for the cli if you go with docopt. I'd love to see argparse expand or docopt
get included...

jlc