Currently, it seems like we require PR branches to be squashed before merging. I think we should encourage contributors to write PRs with multiple commits by lifting this restriction and instead teaching Merge-Queue to do the squashing. I would expect it to use the PR description to write the squashed commit.
<rdar://problem/92648043>
Real world example of where a workflow like this is needed: I'm relanding a change along with a fix. I think it's most logical, both for history and my reviewers, to land two commits: one is the automated `git revert` commit which undoes the revert, and the other applies fixes. Currently, I'm forced to squash them together. As a result, the merged commit doesn't make it clear what was changed.