pub fn write_index_root_marker(root: &Path) -> Result<()>Expand description
Record which search root a relocated index directory belongs to.
A no-op unless the index is relocated via INDEX_DIR_ENV — an in-tree
.ck directory lives under its own root and cannot collide. Callers write
the marker when they create or populate an index directory so a later
check_index_root_marker can detect a basename-hash collision.