Function place_fetched 

fn place_fetched(
    memory: &Path,
    folder: &Path,
    account: &str,
    ready: &[(String, PathBuf, u64)],
) -> Vec<bool>

Sealed files that came (ready: each one’s place in the folder, the name it came under, its size), put in their places in the copy under the step’s lock once the state says they were fetched (State::files): a step never sees one there before, and never takes it for one of this device’s own. Never over a file there (sealed here meanwhile: the same content). Whether each was put there.