UPDATE — moving the stack onto newer versions

Raised by lemonfiber update stack. A bare run changes nothing and says what each step would cost; --confirm takes the steps, behind a backup that is a precondition rather than an offer. Nothing here reaches a registry — what a service would move to ships inside the binary, so the only question asked of the machine is which version each service stands on now.

The release this page is built for does not carry what this part is read from. The next version's page has it.

What each severity and each exit means is on every error by code, beside every other family.