3.6 Customizing built-in variables

Some users want to put all their customizations in use-package declarations, even for variables, hooks, and options that are always available, without loading any package.²

For that purpose, you can use the no-op ‘emacs’ package:

(use-package emacs
  :init
  (setq custom-file "~/.emacs.d/emacs-custom.el")
  (load custom-file)
  (setq frame-title-format "%b")
  :custom
  (use-short-answers t))

This declaration takes advantage of the fact that (featurep 'emacs) always returns true, and has no special meaning beyond that. It simply provides a way to organize your customizations, without loading anything.