Merge branch 'ps/reftable-detach' into ps/reftable-iterator-reuse

* ps/reftable-detach:
  reftable/system: provide thin wrapper for lockfile subsystem
  reftable/stack: drop only use of `get_locked_file_path()`
  reftable/system: provide thin wrapper for tempfile subsystem
  reftable/stack: stop using `fsync_component()` directly
  reftable/system: stop depending on "hash.h"
  reftable: explicitly handle hash format IDs
  reftable/system: move "dir.h" to its only user

diff --cc Makefile
Simple merge

diff --cc refs/reftable-backend.c
Simple merge

diff --cc t/unit-tests/t-reftable-merged.c
Simple merge