I've looked through the Jenkins docs, and I can't find this answer.
I'm played around with it, but my results seem to be somewhat inconsistent.
Is the "block on upstream builds" option transitive?
For example, suppose Project A triggers project B and project B triggers project C.
If A is running and B is triggered, B will not run until A is finished.
If A is running and C is triggered, will C wait for A to finish?