Function virtual_fs::overlay_fs::open_copy_on_write

fn open_copy_on_write<P>(
    path: &Path,
    conf: &OpenOptionsConfig,
    primary: &Arc<P>,
    file: Box<dyn VirtualFile + Send + Sync>
) -> Result<Box<dyn VirtualFile + Send + Sync>, FsError>where
    P: FileSystem,