Notification for discarded changes

We have multiple people accessing our code repository, some times at the same time. The group has varying levels of knowledge for both using git lab and the intent of the code. We have have a daily diff enabled to track code changes and make those changes visible to the entire team.

One issue we’ve encountered is if a user discards someones changes in a merge conflict. If it happens in the same day the daily diff does not capture it. We want a notification enabled whenever a user decides to discard someone elses changes. How do we do this?