expose all diagnostic options

[Dierk]

https://github.com/Frege/frege/wiki/Compiler-Manpage

-comments Generate commented Java code. This makes code generation substantially slower, but can be useful at times.

-nowarn Not recommended. Suppress warnings like those about incomplete pattern matches.

-explain i[-j]

[Ingo60]

Note that the -explain option really only makes sense for a single, specific file - namely one where you got a type error on line i that you didn't understand. You might then repeat compilation with -explain i to get better insight.

[Dierk]

ok, that sounds like an option that can go into the "extra arguments", i.e. those who know about it can supply it like on the command line