Test whether a WIP snapshot commit still applies with merge-tree --merge-base

To check whether a stale branch's last commit (e.g. a 'WIP park' snapshot) still applies onto the current main without touching any worktree, run git merge-tree --write-tree --name-only --merge-base=<snapshot>^ main <snapshot>. This tests only that commit's diff, not the branch's rebased-away history, so conflicts it reports are real. A plain merge-tree against an old, since-rebased branch reports many conflicts that are only rewrite noise. To classify old branches as shipped: in git cherry -v main <branch>, '-' commits are matched by patch-id. For each '+' commit, search for its exact subject with git log main -F --grep="<subject>". Commits rebased with conflict fixes keep their subject but change patch-id. All of these work in blob:none clones without the history-wide fetches that -S/-G/-p trigger.