[PATCH]: shell-complete command

[Clint Adams]

> I'd suggest another dictionary, something like OPTION_ARGS.  Neat thing
> is, if an option does take an argument but a name is not given in
> OPTION_ARGS, you can use some default.  (Maybe the option name?)

If there's going to be a 1:1 correspondence between option name and
argument type, a dictionary for that would be redundant.  That doesn't
allow the granularity to say, "branch -r" takes a single revision,
"diff -r" can take a range, and "merge -r" can take a pair.  In this
case, the real value is in presenting a description to a human;
autocompleting integers is a bit silly.

I'm more worried about things like --format and --root; are they always
going to take the same potential arguments regardless of subcommand?

If so, this can be done more easily.