Currently, in Bitbucket Cloud, a merge check can be added to define the "Maximum number of commits behind destination branch", however, the minimum value that can be set is 1 commit behind.

It would be great to have the ability to define a value of 0 (zero) commits behind, to make sure the source branch is synced with the destination branch before the Pull Request is merged, or have a Merge check specifically to "Branch is up to date with target"