pub fn same_filesystem(a: &Path, b: &Path) -> Option<bool>Expand description
Whether a and b sit on the same filesystem.
The destination normally does NOT exist yet — that is the whole point of asking before creating it — so each path is resolved to its deepest existing ancestor first. Stat-ing the destination itself would answer “unknown” for every question actually worth asking.
None off unix, where the standard library exposes no device id: a rename
across filesystems fails where one within a filesystem does not, so a
migration that assumed “same” would discover it at switch-over time. Saying
“unknown” keeps that decision with the operator.