Function device_files 

pub fn device_files(
    folder: &Path,
    key: &[u8; 32],
    memory: &Path,
    computer: &str,
    stores: &[Store],
    device: &str,
    now_ms: i64,
) -> Option<DeviceFiles>

What “Remove its files” would take out for device, and what stays, for the window to say before you press; None for a device not known here.