As far as I understand : get_new_stable is a git branch of the git web2py-for-fluxflex which allow to import the last stable vesrion of web2py. Yet if you do so you will lost your previously installed app.
I think you should prefer the builtin upgrade button of the admin web2py, but I haven't tried since my project are already running the last stable version. I've always used upgrade builtin button and it always worked on localhost.
