Add `head`, `status`, `log`, `fetch`, `checkout_new_branch`, `pull`, `push`, and `merge` to `RemoteRepository`

This adds a few methods to RemoveRepository. This is a prerequisite for !86.

Legit failures.

assigned to @rymai

changed title from Improve RemoteRepository to {+Add head, status, log, fetch, checkout_new_branch, pull, push, and merge to RemoteRepository+}

mentioned in merge request !86

YAY!

assigned to @rspeicher

Actually, fetch will need to support a :remote arg!

assigned to @rymai

@rspeicher Ok, ready! :P

assigned to @rspeicher

@jameslopez Could you please do a first review of this one? Thanks!

assigned to @jameslopez

mentioned in merge request !179 (merged)

assigned to @rymai

assigned to @jameslopez

resolved all discussions

@rymai awesome work! Left some comments, but nothing major!

assigned to @rymai

@jameslopez Thanks for the thorough review! I'll update after my vacations, in two weeks!

@rymai enjoy your holiday!

mentioned in issue #115

mentioned in issue #116

resolved all discussions

@jameslopez Thanks for the feedback, I've addressed it and created two follow-up issue!

assigned to @jameslopez

thanks @rymai! Left very minor comments but really LGTM.

assigned to @rymai

resolved all discussions

@jameslopez Thanks, I believe I've addressed everything (and now rebased).

assigned to @jameslopez

changed milestone to %10.1

Thanks @rymai! - I don't have access to merge this, though. Assigning to Robert :)

assigned to @rspeicher

@rspeicher Ping!

@rymai I haven't forgotten this one, just blocked on other stuff at the moment!

I do know my general feedback would be "I'd prefer to use Rugged as much as we can, versus shelling out", but I'm not sure yet how possible that will be with the functionality here.

@rymai Sorry for the delay! Couple questions.

assigned to @rymai

resolved all discussions

@rspeicher Thanks a lot for the great review, I improved everything, I'm sure you'll like it! :)

assigned to @rspeicher

@rymai Couple more questions.

assigned to @rymai

@rspeicher Thanks, addressed in 5618122!

assigned to @rspeicher

mentioned in commit phil7/release-tools@26dfb05f