all git commits functions to gitserver client

Created by: mollylogue

Basically delete git/commits.go and git/commits_test.go and copy all of that onto the gitserver client. A lot of these functions referenced each other in this file and it's kind of a nightmare to pull them all apart.

For some reason there are test issues w/ the local git command situation, so figuring out/fixing those is a TODO item (and why this is a draft)

Test plan

All unit tests should pass.