To point something out with the squash merge vs rebase merge policies, we will definitely be enforcing squash merges at least initially because rebase merges require some extra EWS and commit-queue infrastructure.
Recall that WebKit does regression testing for every commit, even if these commits were landed at exactly the same time. With SVN, this fact is unimportant because commit-queue and EWS enforce every commit being atomic. If we wanted to support rebase merges, what we’re really saying is that we want EWS and commit-queue to run on each individual change in a PR, because at least some post-commit infrastructure will do the same. That’s something we could do, but it has some downsides, namely, if contributors are too commit-happy, we will end up using more compute time on each PR.
Jonathan