Below its free-space floor, QuickRust’s cache gives back what the disk is short of and a quarter
of the floor, least recently used first. It counts what it removed as free until the disk
shows it, for a day at most: a filesystem snapshot (Time Machine’s local snapshots, btrfs,
ZFS) keeps freed space from showing, and a collection no longer empties the cache chasing it.
Cargo’s own clean of its downloads runs only while no Cargo that QuickRust started is running,
so cargo package and cargo publish no longer stop in Cargo’s cache tracker.
A collection that fails records what it did, and a command that cannot record that it runs
Cargo stops before running it. The collection log keeps counts by kind and the build
directories it removed, not every path.