Remove -- requirement for roc [FILE] to allow better messaging

[dlsmith]

#5388

roc [FILE] no longer requires --, to allow for better error messaging (see foromat example below). Subcommands are required up front to avoid ambiguity:

$ roc help
Run the given .roc file, if there are no compilation errors.
You can use one of the SUBCOMMANDS below to do something else!

Usage: roc [OPTIONS] [ROC_FILE] [ARGS_FOR_APP]...
       roc <COMMAND>

-- is still required for roc <COMMAND>:

$ roc help test
Run all top-level `expect`s in a main module and any modules it imports

Usage: roc test [OPTIONS] [ROC_FILE] [-- [ARGS_FOR_APP]...]

When roc [FILE] errors, we provide a hint about a possible misspelled subcommand:

$ roc foromat *

This file was not found: /Users/dlsmith/src/roc/foromat

Did you mean to use the format subcommand?

You can run `roc help` to see the list of available subcommands and for more information on how to provide a .roc file.

[bhansconnect]

nit: We may want to skip this message if the possible_typo ends in .roc.

Also, even more optional, if the distance is large, maybe we should skip the message as well.

[dlsmith]

Good ideas! I added the .roc check, but thought I'd be a little more permissive to start when it came to subcommand matching. I included the distance in the return value when I wrote the matching function so it's easy to add additional restrictions later if there are too many false positives. Happy to add it now though if you prefer.

[bhansconnect]

Looks good! Just a nit idea.

[bhansconnect]

Sounds good