upgrade-runtime.txt
My project runs <stack> on <host>. I want to move to <new version>.

Plan the upgrade:
- What changed between my version and the new one that affects code like
  mine. Point at the patterns to search for.
- How to test locally on the new version before touching the host.
- How to switch the version on this host, and how to switch back.
- Dependencies that need updating first.

Give me a checklist in order, with a way back at every step.

Upgrade locally and run everything first. Switching the host's version and finding out live is how a quiet afternoon becomes an outage.