> (defcustom package-selected-packages nil
>   "List of packages to keep installed.
> Packages may also be installed or removed as part of dependency
> resolution, or via `package-autoremove'.  Emacs will try to ensure that
> the packages listed here, along with all their dependencies, are kept
> installed."
>   :group 'package
>   :type '(repeat (choice symbol)))

I like this. Just 2 things:
1. Also say packages are auto added to this list when explicitly installed
(or something like this).
2. Isn't (choice symbol) the same as symbol?