[Pharo-users] Reverting changes in Iceberg

Hi, I was trying to merge changes from a collaborator from github into my local image and, through some flurry of menus I didn't quite comprehend, it seems to have blown away their changes and left me a commit ahead with all of their changes deleted. How can I revert back to their change, which I do see in my history, and continue from there without my erroneous most recent commit? Thanks, Evan