checkAndDownload :: WebDAVConfig -> WebDAVRemoteDir -> FilePath -> MaybeT IO ()
checkAndDownload cfg rdir fpath = do
    b <- liftIO $ doesFileExistInDAV cfg rdir fpath
    guard b
    liftIO $ downloadFile False cfg rdir fpath 
    liftIO $ putStrLn $ fpath ++ " is successfully downloaded"
checkAndDownload :: WebDAVConfig -> WebDAVRemoteDir -> FilePath -> MaybeT IO ()
checkAndDownload cfg rdir fpath = do
    b <- liftIO $ doesFileExistInDAV cfg rdir fpath
    guard b
    liftIO $ downloadFile False cfg rdir fpath 
    liftIO $ putStrLn $ fpath ++ " is successfully downloaded"
checkAndDownload cfg rdir fpath = do
    b <- liftIO $ doesFileExistInDAV cfg rdir fpath
    guard b
    liftIO $ downloadFile False cfg rdir fpath 
    liftIO $ putStrLn $ fpath ++ " is successfully downloaded"