We have a bunch of herald rules to trigger audits along the lines of:
* Differential revision does not exist
* Commit's branches contains master
* Repository's projects include all of some-project
If a commit is pushed to another branch and then to master an audit is not triggered.
Some references to internal stuff in case I need to find it again:
* commit: rSKYFALL036b0846a9fc5d9f6209c5747574ac5d0db84ab1 Lists master and an other branch. No audit triggered
* herald/transcript/487720/ shows 'Condition: Commit's branches contains master' failed