Function brought_already 

fn brought_already(folder: &Path, names: &str) -> bool

The files another device wrote that the sync app just put in the sharing folder (StepService’s watch: their names, “/” between them), each one the pull brought already, the same here as fetched (remote::overlay): whole for a small file, by its size for a larger one (a log’s round, which only grows). Nothing new to read: the folder’s step is left out. Not when nothing is fetched beside the folder, nor for a name not known.