Improve "pkg update" to retain customized ZFS attributes when making a BE clone
The issue #3569 proposes to enhance the "zfs" command with an ability to optionally (as a new command-line option and/or a dataset or pool attribute to set the default action for this feature) replicate customized ("received" and "local") ZFS attributes from an origin dataset (whose snapshot is used) to the new clone; this feature should optionally be used in "beadm" in particular. And by extension, creation of BE clones with the "pkg" command should also use this improvement (optionally).
One practical use-case regards "split-root" installations with separate compressed datasets for the /usr filesystem - when "pkg upgrade" creates a clone of the target BE, the cloned datasets inherit attributes (including "compression") from rpool/ROOT, and the subsequent writes of upgraded package data becomes not so compressed as the user intended it to be. Workarounds are possible today (beadm clone, apply zfs attributes, run "pkg -R /a update") but not so convenient as a single-shot automated operation.