Baxter Installation on ROS groovy

edit

I am trying to install Baxter on ROS groovy from catkin workspace where the SDK resides, and use wstool to install and update. This is waht i am supposed to do:-

    $ cd ~/ros_ws/src
    $ git clone git@github.com:RethinkRobotics/baxter_simulator.git
# IMPORTANT EARLY-DEV-RELEASE STEPS:
    $ cd baxter_simulator
    $ git checkout early_interface_dev
    $ cd ..
    $ wstool init # need to do this only if this is a new workspace where this command was not executed before.
    $ wstool merge baxter_simulator/baxter_simulator.rosinstall
    $ wstool update

But after i type in <git checkout="" early_interface_dev=""> i get this error message. please explain the reason and solution.

sa@svs-FX6860:~/catkin_ws/src/baxter_simulator$ git checkout early_interface_dev
error: pathspec 'early_interface_dev' did not match any file(s) known to git.