Support `rls --version`

[alexcrichton]

Right now the rls executable we're going to start shipping doesn't support rls --version, but we've got a relatively standard format between rls/cargo that should be supported. Cargo's looks like this and we probably want the RLS logic to look similar.

[alexcrichton]

cc #40584, @nrc, @jonathandturner

(you may wish to open a tracking issue in the rls repo to track this)

[sophiajt]

The RLS currently has a --version flag. Is this bug tracking it landing in rustup?

[sophiajt]

(lol, just noticed the date of the bug...)

[alexcrichton]

Aha yep! Just ran this:

$ rls +nightly --version
rls 0.1.0 (38ca9b7 2017-05-14)

Looks great to me! The only missing piece I believe is the "-nightly" or "-beta" piece. @jonathandturner do you know the right person to cc about that?

[sophiajt]

I'd CC @nrc since he's overseeing RLS and can handle it

[nrc]

I added -nightly to the version string. The RLS is always nightly for now since we are not going though beta, etc. at the moment. Is that going to work for Rustbuild?

The RLS currently has a --version flag. Is this bug tracking it landing in rustup?

AIUI Rustbuild should actually use the flag, rather than do whatever placeholder thing it does at the moment.