There is a Docopt implementation in Rust[1], which is used by Cargo. It tracks master and is regularly updated.
Interestingly, I've found people either love or hate Docopt, so maybe you knew about it but don't like it. :P
/shameless plug
[1] - https://github.com/docopt/docopt.rs
It is broken now, but with the collection reform landing, what isn't broken.
It's passing now that Travis updated to the new nightly.
(But yup, it was collection reform.)
There is a Docopt implementation in Rust[1], which is used by Cargo. It tracks master and is regularly updated.
Interestingly, I've found people either love or hate Docopt, so maybe you knew about it but don't like it. :P
/shameless plug
[1] - https://github.com/docopt/docopt.rs