Luckily it looks like the upgrade story of Ghost itself has been nailed down since I first set up a Ghost blog 5 years ago.
The Ghost CLI tool is fairly well thought out and includes possibly my favorite command-line tool argument ever. (see the first one below)
# ghost help ghost [command] Commands: ghost buster Who ya gonna call? (Runs `yarn cache clean`) ghost config [key] [value] Configure a Ghost instance ghost doctor [categories..] Check the system for any potential hiccups when installing/updating Ghost ghost install [version] Install a brand new instance of Ghost ghost log [name] View the logs of a Ghost instance ghost ls View running ghost processes ghost migrate Run system migrations on a Ghost instance ghost restart Restart the Ghost instance ghost run Run a Ghost instance directly (used by process managers and for debugging) ghost setup [stages..] Setup an installation of Ghost (after it is installed) ghost start Start an instance of Ghost ghost stop [name] Stops an instance of Ghost ghost uninstall Remove a Ghost instance and any related configuration files ghost update [version] Update a Ghost instance ghost version Prints out Ghost-CLI version (and Ghost version if one exists)