Oh you work at Atlassian! I wonder if the PR I recently had accepted into "Auto Unapprove Plugin" will affect you! (I get the sense Atlassian uses that add-on internally).

https://bitbucket.org/atlassian/stash-auto-unapprove-plugin/...

(Issue #15 in particular - base unapprove on: git diff target...source | git patch-id).