This page describes in short the Addons that are deployed on Bitbucket. Configuration diverged from default are present. 

Auto Unapprove for Bitbucket Server

This addon removes all approvals from a Pull Request (PR) when a change is applied on the branch after. In combination with setting a minimal number of approvers on PR a merge of unapproved code is avoided.

Information: can be found in the Atlassian marketplace