Autocomplete generation

[Slakah]

I've never really looked into it in earnest, but it feels like it could be cool to generate a bash autocomplete file from a supplied com.monovore.decline.Command. This functionality feels like it would be a separate module though.

[bkirwi]

Indeed! I think this would be a pretty natural fit.

I imagine this could mostly be done in a seperate module, like you suggest, just by inspecting the command. The one thing that might be tricky is allowing tab-completion for values... given a Opts.option[Path](...) it really feels like you should be able to tab-complete files, but we don't hang on to enough information to thread that through to a bash autocomplete file. One path might be to: figure out a small ADT to represent completions, add a field to the Opts types that have arguments, and add another method to Argument to set a default value.

I'm unlikely to implement this myself anytime soon, but I'd be happy to review contributions of this shape if you / someone else is interested!

[kubukoz]

Rel: #250 (tbh I'd suggest merging the two)

[bkirwi]

Sure - let's close this one since it's had less discussion.