OpenShift 4 Upgrade Paths
For OpenShift 4, the upgrade paths are kept in the cincinnati-graph-data repository as YAML files and then exposed via an API.
There is a Red Hat Solution describing how this data can be queried via api.openshift.com and how you can use this data in your automation:
$ curl -sH 'Accept:application/json' 'https://api.openshift.com/api/upgrades_info/v1/graph?channel=fast-4.2&arch=amd64' | jq .
While this data is quite helpful for automation (the Solution also describes helpful queries), it is not very nice to look at the raw data. If you are looking for a graphical presentation of that data, you should check out this wonderful website that is maintained by a Red Hat colleague with hourly generated data: www.ocp-upgrade.net