Can squash commits be signed?

[Kai Günster]

My scenario is this: I have repositories where we work with pull requests. In the future, we want all commits in those repositories to be signed. We also want to use one of the the Squash merge strategies because it saves us from manually squashing the source branch first.

I fully expect the answer to be no because I don't see how it would work, but I want to know for sure: is there a way to have the squash commit be signed, either by the user that triggered the merge or with a special key configured in Bitbucket?