The main use case for us is to do a code review vs one branch, then merge to another. For example, I am working on (yet unmerged) branch A, and my colleague wants me to review his changes that depend on my work. We want them to be to request a code review vs branch A, then submit a PR to master
after A is merged. Keeping a PR for master open, as the answer suggests, will unnecessarily pollute the code review with code from branch A which is not yet in master. —
Alex O 42 secs ago