Follow-up to the cherry-picked #69063: egilewski's review found that the
_dir_has_any_entry(parent) guard treats ANY entry in the mount point's
parent as proof the volume is attached — but unmounting exposes the
UNDERLAY directory's own files (e.g. a .keep placeholder), so a populated
underlying mount-point dir still classified the project as an orphan and
deleted its ref/index/metadata. Reproduced on both main and the PR head.
Attachment evidence is now positive instead of circumstantial:
* _volume_evidence() records the parent directory's (st_dev, st_ino)
identity in the project's metadata while the workdir is observably
live (at _register_project/_touch_project time). A mount point
resolves to the mounted filesystem's root while attached and to the
underlay directory after detach — same path, different directory,
different identity.
* _workdir_is_observably_gone() now requires the parent visible at
prune time to match that recorded identity before the populated-parent
check can classify an orphan. A mismatch means a different directory
(the underlay) is showing through — a detached volume, not an
observed deletion.
* Metadata without a recorded identity (written by older versions) is
never orphan-classified — unsure never deletes; the retention/stale
rule still reclaims genuinely abandoned projects off last_touch.
* The frozen pre-v2 layout has no metadata channel for the identity, so
it keeps the structural checks only (require_parent_identity=False).
* A failed evidence probe on re-registration preserves the previously
recorded identity — stale evidence can only make pruning MORE
conservative.
Windows: st_dev/st_ino of 0 (filesystems without file IDs, some network
shares) is treated as "no evidence recorded", which falls into the
conservative never-orphan path. os.path.ismount and Path.stat are
cross-platform; no POSIX-only calls added.
tests/tools/test_checkpoint_manager.py: adds egilewski's exact
regression (checkpoint history for mnt/volume/project, detach exposes
mnt/volume/.keep, prune with orphan deletion enabled → NOT deleted;
fails on the bare cherry-pick, passes with this fix), plus
no-recorded-identity conservatism and probe-failure identity
preservation. His absent-parent/empty-parent/retention/genuine-deletion/
live-project controls all still pass.
Reported-by: egilewski (review on #69063)
1cfc3425af