The supervision was already right — a clean exit means the host stood aside and
the launcher runs what is on disk, failures are counted, and a rollback happens
at the limit. Two things made it dead code: nothing told the running host a
successor was waiting, and the rollback resolved its known-good version through
pacman, which no machine here uses and which two of three operating systems do
not have.
Keeping a version rather than a path was the clue. Versions live side by side in
directories named for them; the newest runs; the running one stands aside between
reconciles; a reconcile that completes records itself and retires what is older
than its predecessor; rollback starts that predecessor. No new resource kind and
nothing new on the bus — an archive already fetches by digest, and the path
written is never the path executing.
Answers issue 142.
jschoubben