Thanks to @Mystery Incorporated who posted his upgrade script a couple of weeks back. I couldn’t understand all the Git commands so I re-did the entire thing in Bash because it was quicker than learning git. Sad, I know.
Here it is, please take it, torture it, improve it and let me know what could have been done better
https://github.com/adamphetamine/fleetdm/blob/main/fleet-upgrade.sh