This is a follow-up to
MNG-4418. The model/settings validation that has been put in place to avoid metadata corruption of the local repo by a remote repo that misuses the same id doesn't help when plugins create repository instances on their own as with the maven-deploy-plugin in combination with its altDeploymentRepository parameter.
Using such a setup, the JGit folks ended up with builds that weren't able to resolve local snapshots that had just been installed seconds before. We need to improve the diagnostic output to more easily detect this kind of metadata corruption and gracefully recover from it.