wrap option handling in a function

[suvayu]

I considered using Val but it doesn't really work since it's also
required to invoke the fuction with Val{value}, instead of just
passing value (unless I misunderstood how this works).

So I essentially factored out the logic to a regular function, and
wrote tests to cover all behaviours.

Thoughts?

[suvayu]

Looks like I misunderstood how to use Val :-p