Mod rewrite at top level to sub directory

Hi all, I’m very new to url rewriting. I’ve been able to get very simple rewriting to work (one particular file rewritten as another file), but now I’m trying to do what I actually want my site to do:

rewrite all urls to the same url with an extra directory in it. For example, => =>

Why am I doing this? Because I want to be able to have a simple staging vs production scheme: I can upload a new version of my site in the folder “stage” at the document root. Then I can go to to test out the new code (btw, I think this means I have to have a special rule that says to leave alone any requests to /stage). Now, when I’m ready to “deploy”, I just rename “stage” to “prod”.

Thanks for any advice!