mcman version vs mcman --version

[tippfehlr]

I tried to run ncman --version, just to see it fail.

Just for the sake of correctness, I would propose:

1. mcman --version printing just the current version
2. mcman self-update updating mcman. However, that shouldn’t work when installed via some package manager, so I would propose to check if the executable is /usr/bin/mcman, and otherwise continue to self-update (just like rustup: rustup self update is disabled when installed via package manager).

EDIT: just had a look in the code and saw that mcman version doesn’t update mcman.
Cargo handles cargo --version and cargo version the same; I think it would be nice to do the same.