Over at the Emacs subreddit, attrigh asks if there is some way of refreshing the results of an occur when the underlying buffer changes. I’ve never run into a use case where that would be helpful but it’s easy to see how it could in many workflows. I didn’t know the answer off the top of my head but I probably would have stumbled on the answer just by doing the expected thing if I had needed an occur refresh.
In any event, the answer is to type g just as you do in similar situations to rebuild the results buffer of some command. I doubt this tip is going to save anyone hours of time but it is a handy thing to know for when your underlying buffer changes and you really don’t want to retype that long, nasty regex.