Print command line syntax

[theimowski]

This is something we could make use of in fsprojects/Paket#514 when generating docs

[eiriktsarpalis]

Thanks. Couple of thoughts:

I think that an argument with at least two names and is mandatory will render like this:

--arg-name|--alt-arg-name <string>

Is this to be expected?

Also, [<Rest>] arguments are not presented in the printed syntax. Compare with https://github.com/nessos/UnionArgParser/blob/master/src/UnionArgParser/UnParsers.fs#L38

Could you address these issues in the PR?

[theimowski]

Sure, will do

[eiriktsarpalis]

Thanks!

[theimowski]

an argument with at least two names and is mandatory will render like this:

(--arg-name|--alt-arg-name) <string>

[<Rest>] is handled with ...

Also, I ordered the args by [<First>] and then by [<Rest>]

[eiriktsarpalis]

Merged, thanks!