Custom merge checks allow you to cause a pull request merge to be vetoed. The same functionality can also be achieved using a Conditional Merge Check. However, custom merge checksare most useful when you want to dynamically generate the veto message.
Enforcing reviewers in several timezones with dynamic veto message
The intention of this hook is to ensure that the author and reviewers are in at least three time zones, as a mechanism of ensuring people in different offices are aware of code changes.