`cabal --version` should report the commit used for developement builds.

I often build cabal from source and today I realized unless i keep the repo around and on a given commit it's hard to find out what commit I'm running with.

Might be useful if it said something like:

`cabal-install version 3.17.0.0 (<hash>)` for development builds?

Or perhaps it should be a new line in the --version output to avoid messing with existing version regex too much.