tf.exe get command show All files are up to date,but no files are downloaded in script

@echo off

set base=C:\autobuild\workspace

set cwRsync=C:\tools\cwRsync
set PATH="C:\Program Files (x86)\Microsoft Visual Studio 11.0\Common7\IDE";%PATH%;%cwRsync%\bin
set h=%time:~0,2%
set h=%h: =0%
set currtime=%date:~0,4%%date:~5,2%%date:~8,2%%h%%time:~3,2%%time:~6,2%
set workspace=%~n0_%currtime%
set currentdir=%cd%

set remote=192.168.30.153::tfs/

set collection=/collection:http://192.168.30.131:8080/tfs
set login=/login:zhang.san,123456

echo url=%url%


if exist %base%\%workspace% rd /S /Q %base%\%workspace%

set workfolder=%base%\%workspace%
mkdir %workfolder%


rem tf workspaces %collection% %login%
tf workspace /new /noprompt %workspace% %collection% %login%
tf workfold /map "$/" %workfolder% %collection%  /workspace:%workspace% %login%
cd /d %workfolder%
tf get %url% /recursive %login%
tf workfold /unmap %workfolder% /workspace:%workspace% %login%
tf workspace /delete /noprompt %collection%  %workspace% %login%

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in this script, tf get command display message "All files are up to date" ,but there is nothing found in %workfolder% ,why and how to resolve it?

tf.exe version: 11.0.50727.1

Visual Studio Ultimate 2012  11.0.50727.1 RTMREL

OS: windows server 2008 R2