how do I remove a workspace from the package path

edit

Hello

I've set up two workspaces to try to run two forks of the same project (maybe not the correct way, but it happened), and now I can't revert to using the previous workspace again.

I've commented out the line

source ~/alt_catkin_ws/devel/setup.bash

from my bashrc, but

echo $ROS_PACKAGE_PATH

still lists both workspaces, and rosrun will only run using alt_catkin_ws

Using rosws hasn't helped so far, I've tried

rosws set catkin_ws
cd catkin_ws; rosws set ~/catkin_ws

and I get this error:

ERROR in config: Command requires a target workspace.

Googling this hasn't really provided much information. I don't know what I'm doing, help!