In the pull request merge checks it would be useful if we had an option we could toggle to check if the branch is behind the destination branch in commits and not allow the merge until it's rebased (behind==0).  If the "minimum successful build" check is also enabled this would ensure that the merge would keep the main regression stable.  This would be a simple solution/option for small bitbucket projects to make sure that the pull request changes are compatible with code that has been merged prior.  I know there is also options like "flights" where you take all incoming PRs into a single merge but for small projects and frameworks it's overkill.