Problem checking out navigation 1.8.3

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Hi, I was trying to checkout navigation 1.8.3 from github to my workspace. The commands I used are,

rosws set navigation --git https://github.com/ros-planning/navigation
/tree/navigation-1.8.3
rosws update

However, when doing update, I received the error:

[navigation] Fetching https://github.com/ros-planning/navigation
/tree/navigation-1.8.3 (version None) to /home/chengxiang/sim_workspace/navigation
WARNING [vcstools] Command failed: 'git clone --recursive https://github.com
/ros-planning/navigation/tree/navigation-1.8.3 /home/chengxiang/sim_workspace
/navigation'
 errcode: 128:
fatal: https://github.com/ros-planning/navigation/tree/navigation-1.8.3/info/refs 
not found: did you run git update-server-info on the server?
[/vcstools]
Exception caught during install: Error processing 'navigation' : [navigation]   
Checkout of https://github.com/ros-planning/navigation/tree/navigation-1.8.3 
version None into /home/chengxiang/sim_workspace/navigation failed.

ERROR in config: Error processing 'navigation' : [navigation] Checkout of   
https://github.com/ros-planning/navigation/tree/navigation-1.8.3 version None 
into /home/chengxiang/sim_workspace/navigation failed.

I am not familar with github at all so I don't have a clue what's wrong.Could anyone please advise? I am using ROS-fuerte on Ubuntu 12.04. Thanks in advance.