FreeBSD: pkgbase: major upgrades

<https://gist.github.com/grahamperrin/a58edbb8587af513a154ac01d922f611#file-pkgbase-major-upgrade-md-readme>

― a rough guide, for alpha testing on AMD64.

From <https://redd.it/1nlo8lp>:

❮ An obvious response to the roughness: it's more complicated than legacy freebsd-update(8) (for FreeBSD 14.3-RELEASE). True; this is for alpha testing.

Please read the preamble before anything else. If you have any question, please don't hesitate to ask. ❯

#FreeBSD #pkg #pkgbase #alpha