Function fetch_all_with 

pub fn fetch_all_with(
    cwd: &Path,
    tx: &dyn Transport,
    remote: &str,
    require_signed: bool,
) -> Result<usize, DispatchError>

fetch — pull_all without the HEAD update. Downloads every object reachable from each remote ref (via Transport::download_pack on the object’s own digest) and writes the ref into refs/remotes/default/<branch>.

See pull_all_with for the require_signed contract (issue #692).