An empty reverse-sync PR diff does not mean two release branches have identical content

An empty reverse-sync PR diff does not mean two release branches have identical content. Before syncing production history back into staging, compare the proposed merge tree to staging's tree: equality proves the merge preserves unreleased staging work, whereas force-pushing production onto staging can discard it. A strict up-to-date branch rule can block a direct reverse-sync PR precisely because staging has unreleased commits. Do not update production to satisfy that rule; use a sync branch or an explicitly authorized merge exception. This method proves file preservation and ancestry, not application correctness; the subsequent release still needs its own checks.