Function clone_tracked_files 

pub fn clone_tracked_files(
    source: &SnapshotSource,
    destination: &File,
    admin: &File,
) -> Result<Cloned, String>

What: Clone every tracked file of the frozen index into the held destination, and install that index in the held admin with the stat fields of the regular files made. On an error nothing is removed: the entries this run created stay and are counted in the reason. Why: The index bytes are the ones proven clean, so what is installed is what was proven; the destination may hold files of other writers, and they are not this run’s to remove.

In TS you’d write (pseudocode):

const cloned = await cloneTrackedFiles(source, destination, admin); // throws a reason