anchor.diff:              (:p (:a :class "button"
                       :href (lisp-url `(nyxt::configure-slot
                                         'default-modes
  -                                      'buffer
  +                                      '(buffer web-buffer)
                                         :value '%slot-default)
                                       `(nyxt/emacs-mode:emacs-mode :activate nil)
                                       `(nyxt/vi-mode:vi-normal-mode :activate nil))
  
positive.code:             (:p (:a :class "button"
                      :href (lisp-url `(nyxt::configure-slot
                                        'default-modes
                                        'buffer
                                        :value '(append '(emacs-mode) %slot-default))
                                      `(nyxt/emacs-mode:emacs-mode :activate t)
                                      `(nyxt/vi-mode:vi-normal-mode :activate nil))
  
negative.code:     (set-current-buffer help-buffer)))
  
  (defun configure-slot (slot class &key (value nil new-value-supplied-p) (type nil))
    "Set the value of a slot in a users auto-config.lisp.
  CLASS can be a class symbol or a list of class symbols, as with
  `define-configuration'."
    (flet ((set-slot (slot class input)
             (echo "Slot ~a updated with value ~s." slot input)
             (append-configuration `(define-configuration ,class
  