As of now, we are using the Github PRs to merge changes, we try to keep the Git history clean and avoid merge commit to pollute our code history while upstreaming new commits to Apache repo. the blog states why and how to avoid merge commits very clearly.
http://www.kerrybuckley.org/2008/06/18/avoiding-merge-commits-in-git/ The problem is if we received multiple pending PRs, we have to notify all owners of remaining PRs to rebase their commits every time when a PR commit got upstreamed. Any idea about how to avoid merge commits while not bother PR owners to rebase their changes once their PR get submitted? Thanks!