This container can be pulled via:
  docker pull registry.opensuse.org/home/pushman/bci/cr/tumbleweed/containerfile/opensuse/alertmanager:0.28
  docker pull registry.opensuse.org/home/pushman/bci/cr/tumbleweed/containerfile/opensuse/alertmanager:0.28.1
  docker pull registry.opensuse.org/home/pushman/bci/cr/tumbleweed/containerfile/opensuse/alertmanager:0.28.1-6.57
  docker pull registry.opensuse.org/home/pushman/bci/cr/tumbleweed/containerfile/opensuse/alertmanager:latest

Set DOCKER_CONTENT_TRUST=1 to enable image tag verification.