Here's what I'm curious about that is not mentioned at all:
How do they manage deployment to staging? At my company we typically deploy topic branches directly to staging, but we have fewer developers and slower pace. If multiple people need to deploy topic branches we set up an ephemeral staging branch that merges the multiple topic branches together, but I can imagine that getting super hairy on a team the size of GitHub's.
Do they just mostly deploy directly to production, thus severely minimizing staging contention?
it depends. when staging is in a good state we'll simply ask if anyone is using it. you can see a few deployments to staging in that screenshot i posted i believe. however, if the developer judges that a ci pass is good enough, a deployment directly to prod after they get the ci green light is also common.
this is also one of the benefits of deploying via a chat room - you can ask if you're going to be stepping on anyone before you do it.
How do they manage deployment to staging? At my company we typically deploy topic branches directly to staging, but we have fewer developers and slower pace. If multiple people need to deploy topic branches we set up an ephemeral staging branch that merges the multiple topic branches together, but I can imagine that getting super hairy on a team the size of GitHub's.
Do they just mostly deploy directly to production, thus severely minimizing staging contention?