Advanced PR checks

Due to specific conditions, it is possible to merge more than one pull request. See this example:

1. Make some commits on a branch B and create a PR1 from B->A but don't merge it yet
2. Merge branch B into another branch C, make some new commits to branch C (possibly undoing the original commits on branch B)
3. Create a PR2 from branch C->A and accept/merge it.
4. PR1 will automatically be merged as well, because technically all its commits are within PR2.

It would be useful to have the following:

A) Show a warning message that two PRs are going to be merged at the same time, to prevent the confusion that arose.
B) Explain a manual copy method of cherry-picking commits to fix unintended consequences of a merge (may need to be a separate guide to refer to)