Add merge check for sync now

In "Edit branch permissions" (see attached "bitbucket checks required.png") I'd like one more tick box under merge checks. The merge check would be something like "Sync not required".

When enabled merging would be prevented if "sync now" message appears in the source branch's commits list (see attached "sync now.png").

Currently merging is only prevented if there is a merge conflict. I'd like it to be prevented if any all cases.

Github has recently introduced this feature and I'm hoping Bitbucket will too.