Code review comment for lp:~jimbaker/pyjuju/ssh-passthrough

Nice work jim. lgtm, a minor

[0]

+def parse_passthrough_args(args, flags_taking_arg=frozenset()):

the frozenset seems like overkill when an empty tuple suffices.

[1]

re the same function.

Is supporting long options just a matter of an additional conditional
clause for peeked.startswith("--") ? If so it seems better to just
implement support for it now.

[2] re the conflict william brought up, experimenting with the ssh cli it doesn't actually appear to be a problem in practice the user specified option will take precedence as its specified last.