FWIW, my leaning is towards more granularity. I think it might help me to tune the signal-to-noise ratio a bit in my email. If anything I think pgm_communication sounds too broad. In particular, I’m thinking that if there were a pgm_interviews, I would unfollow it. 
I’m assuming that I might still be able to access the repo history through its web interface even if I’m not following a particular repo?