pub fn drift(dir: &Path) -> DriftReportExpand description
Judge every *.toml in dir against EMBEDDED, without changing
anything: seeding writes if-absent and never prunes, so a directory an
operator keeps drifts from the shipped set in three ways at once, and this
is the read that names them.
Pure over the directory listing and the embedded set. A missing or unreadable directory yields an empty report rather than an error, which reads as “no drift” — the caller has nothing to say about a directory that is not there (NFR 10).