Actually it's a default key binding in the (yet unreleased) Emacs 28. project.el has a lot of nice improvements in the upcoming version of Emacs. (I imagine the

Actually it's a default key binding in the (yet unreleased) Emacs 28. project.el has a lot of nice improvements in the upcoming version of Emacs. (I imagine the grandparent comment author just checked the version tag in `C-h k C-x p f' to see when it was released, but currently on Emacs HEAD the keybinding doesn't have a proper version tag - that's a big, albeit minor)