try to reduce the complexity & number of API calls to controller on each git push

[arschles]

As of this writing, we make 3 calls. After #122, it may be 4. If we can batch, pipeline, or use a different wire protocol (that option would probably require the most changes by far), we should.

[arschles]

One optimization after #122 is done is to have builder keep a cache of SSH keys on-disk and only request key change deltas since a last version.

[smothiki]

This is what I feel git push and updating keys have to happen asynchronously. keys:add is a complete different operations as git push is . Keys add has already happened by the time we do git push .

[arschles]

@smothiki they can still happen asynchronously (see the reaper discussion above), but we need to have the synchronous call so that the keys:add operation is strongly consistent.