pkg upgrade (was: freebsd-update and pkgbase)

Baptiste's presentation a decade ago, before my time, included the end 
user perspective for upgrading the system:

pkg upgrade

Subject lines of the January 2016 update, and the March call for testing 
included:

pkg(8)

– and the install command was for installation. I imagined nothing other 
than the upgrade command for upgrading.

Approaches that are coherent are highly valued.

pkgbase, as originally intended, can be embraced.

Packages, tools, and conventions; with 'pkg upgrade' naturally amongst 
the conventions.

<https://www.bsdcan.org/2015/schedule/attachments/321_packaging-base.pdf#page=26>

<https://lists.freebsd.org/pipermail/freebsd-pkgbase/2016-January/000000.html>, 
first sentence:

> … package and upgrade the FreeBSD base system using pkg(8). 

<https://lists.freebsd.org/pipermail/freebsd-pkgbase/2016-March/000032.html>