Public pull request previews no longer get production values, and no
preview falls back to production variables. Existing previews were
deployed with these values; for example, their databases were
initialized with the production password, so they broke on redeploy.
Previews that exist at the upgrade get keeps_production_values and
keep the earlier behavior. Previews created later do not. Server
transfer moves the flag.
Andras Bacsai
2dcf8eeca3