Git repo fetching seems to slow down over time

This occurs with both the master's fetching from the remote and the slaves fetching from either the master or the remote. If ignored a fetch that should take a few seconds can increase to a minute or more. Manually recloning the repo seems to fix the problem.

I suspect this is an issue with git repos either needing to be periodically cleaned or recloned, but we should do some proper investigation to make sure.