rustic-fmt should allow universal optional

[psibi]

This should allow it to pass custom arguments etc.

[psibi]

As an workaround I have set rustic-rustfmt-args now, but I would like to have the ability to pass custom arguments.

[CeleritasCelery]

I honestly think it would be helpful to have consistent interfaces to all the functions. Things like overriding the arguments or hooks have to be implemented for each one. It think it would be nice to something like rustic-define-command macro that sets that all up. It would also make it easy to add your own commands like Miri.

[psibi]

I agree and I think it's going to be much nicer than what we have now. But from what I understand, that's a relatively huge amount of work to make it backward compatible with what we have.