gpush should output commit hashes

[robnagler]

I'm now getting (Shell command succeeded with no output) instead of the commit hashes. It would be nice to see commit hashes. This requires saving the output in a variable instead of tossing it.

[e-carlin]

Just saw

To have this happen automatically for branches without a tracking
upstream, see 'push.autoSetupRemote' in 'git help config'

[robnagler]

Added in git 2.37.0 which is pretty recent. Won't work on older versions or the mac