Reduce noise in gps rr

[Alizter]

When doing gps rr we typically get a very noisy output and this can be overwhelming to users. When using gps brr or eventually the proposal in #255, this issue gets multiple times worse. There are two main issues here:

1. We output the output of Git. This includes all the noisy output about pushing to remotes.
2. We have a very noisy hook message.

The second is not a problem once you've setup hooks, so perhaps that can be dealt with at a later time. The first is more immediately concerning for us.

I propose to change the output so that we only print relevant information for the use. Pretending that gps rr can batch, it would look like this:

gps rr 1-2 3 4-6
Successfully pushed 1-2
Isolation error on 3
Successfully pushed 3-6

We can do this by capturing the output of git and perhaps displaying it later if something goes wrong. Most of the time it is irrelevant however.