Add proper error handling for conflicting flags

[SpyrosRoum]

This closes #55

[marcospb19]

One question, @SpyrosRoum, do you think that removing some error enum variants and just using FinalError for all the errors that never repeat is a bad decision?

The biggest problem in ouch's code structure in my opinion has been error treatment (for some time now), what do you think about it? Do you have any suggestions?

Asking because you have already seen how our treatment works, and I think I would need a bit of feedback before making any reasonable decision.

[SpyrosRoum]

Honestly when you are making an app and not a library it doesn't often matter what the specific error is since most of the times you just want to return a nice message to the user and call it a day.
Personally when I am making an app I'd use something like anyhow or eyre.

In this particular case you can do what you said and if that's not enough then use one of the crates I mentioned earlier. You can still keep the builder pattern for the error but get rid of most of the other errors.

Btw if you need help with implementing this, or the move to clap you mentioned at some point then open an issue and let me know, I'd be happy to help.

[marcospb19]

Thanks for the input!

@dlight suggested anyhow and eyre too, I ended up being inspired by the usage of user-error to create our own builder to display error with our custom syntax, error causes and the hints on how to fix it (the hints being inspired from rustc compile errors).

I'll make sure to open the issues 🙂.

[marcospb19]

@SpyrosRoum #105 is now open if you wanna pick it 👍.