Bitbucket currently offers various merge strategies, where it can fast-forward the target branch to the tip of the merged branch, or force to create a merge commit.

I feel like there is a merge strategy missing : fast-forward (if possible) if the PR has only one commit, and merge no-ff if the PR has more than one commit.

This way, most fixes with only one commit would keep the history linear, while PRs with many commits would be merged with a merge commit, grouping the related fixes together.