Packit now consumes org.fedoraproject.prod.pagure.git.receive fedmsg messages, but unlike previously used org.fedoraproject.prod.git.receive there is no indication whether a push is a result of a pull request merge. It turns out there is no reliable way to get that information and to find the matching pull request. We could start consuming also org.fedoraproject.prod.pagure.pull-request.closed messages but we would still need to exclude related org.fedoraproject.prod.pagure.git.receive messages (as a PR merge generates both) and that would be prone to race conditions, so adding ID of a pull request whose merge triggered the event directly to org.fedoraproject.prod.pagure.git.receive payload seems like a better solution.