Out of curiosity, I see that opening a PR triggers an automatic branch build, when the code is merge into master is your build process repeated?

If not, which is what the diagram implies, how do you handle two branches with two PRs trying to get merged in, since there is a chance that they will create conflicts with each other. Do you force branch tests sequentially?

We don't allow stale merges so each branch must be fully up to date with master before it can be metged.

This is a bit of a pain in busy repos