Tweak the `savehist-mode' setup

README.org

@@ -228,9 +228,9 @@ of [[info:emacs#Saving Customizations][saving customizations (info)]].
  recentf-max-saved-items 100
  recentf-mode t
  save-place-mode t
+ savehist-mode t
  scroll-bar-mode nil
  tab-always-indent 'complete
- tab-width 8
  tool-bar-mode nil
  tooltip-mode nil
  url-cookie-trusted-urls nil
@@ -978,9 +978,11 @@ Emacs.  Try {{{kbd(C-h o)}}} instead of {{{kbd(C-h f)}}} or {{{kbd(C-h v)}}}.
 (with-eval-after-load 'help-fns
   ;; ChatGPT recommends to require `shortdoc' contrary to the
   ;; `shortdoc-help-fns-examples-function' documentation string.
-  (require 'shortdoc)
+  ;; BUG#71537: "emacs -Q" does not need the `add-hook' form. Note:
+  ;; `add-hook' should append `shortdoc-help-fns-examples-function' to
+  ;; `help-fns-describe-function-functions'.
   (add-hook 'help-fns-describe-function-functions
-            #'shortdoc-help-fns-examples-function)
+            #'shortdoc-help-fns-examples-function 'append)
   (setopt help-enable-symbol-autoload t))
 #+end_src
 
@@ -1352,10 +1354,11 @@ completion in any buffer.
 :END:
 
 Listing [[lst:enable-vertico-mode]] configures and enables =savehist-mode= and
-enables =vertico-mode=.  The documentation src_emacs-lisp{(describe-function
-'savehist-mode)} why it is best to turn on =savehist-mode= in the Emacs init
-file.  BUG: Adding ~eww-history~, ~register-alist~, ~regexp-search-string~, or
-~search-string~ to ~savehist-additional-variables~ fails to save the relevant
+enables =vertico-mode=.  The src_emacs-lisp{(describe-function 'savehist-mode)}
+documentation explains why it is best to turn on =savehist-mode= in the
+=user-init-file=.  Listing [[lst:prune-file-name-history]] allows to prune
+non-existing files from the file name history.  BUG: Adding ~eww-history~ or
+~register-alist~ to ~savehist-additional-variables~ fails to save the relevant
 histories.
 
 #+caption[Enable =savehist-mode= and =vertico-mode=]:
@@ -1363,8 +1366,8 @@ histories.
 #+name: lst:enable-vertico-mode
 #+begin_src emacs-lisp -n :results silent
 (with-eval-after-load 'savehist
-  (setopt savehist-additional-variables '(kill-ring search-ring))
-  (savehist-mode +1))
+  (setopt savehist-additional-variables
+          '(command-history kill-ring regexp-search-ring search-ring)))
 (when (and (ensure-package-installation 'vertico)
            (fboundp 'vertico-directory-delete-char)
            (fboundp 'vertico-directory-delete-word)
@@ -1378,6 +1381,22 @@ histories.
     (keymap-set vertico-map "RET" #'vertico-directory-enter)))
 #+end_src
 
+#+caption[Prune non-existing files from =file-name-history=]:
+#+caption: Prune non-existing files from =file-name-history=.
+#+name: lst:prune-file-name-history
+#+begin_src emacs-lisp -n :results silent
+(defun prune-file-name-history ()
+  "Prune non-existing files from `file-name-history'."
+  (interactive)
+  (let ((old (length file-name-history)) ok)
+    (dolist (name file-name-history)
+      (when (file-exists-p name)
+        (push name ok)))
+    (setq file-name-history (nreverse ok))
+    (message "Pruned `file-name-history' from `%S' to `%S' files"
+             old (length file-name-history))))
+#+end_src
+
 #+attr_latex: :booktabs yes :float table
 #+caption[Vertico key map bindings]:
 #+caption: Vertico key map bindings.
@@ -4962,7 +4981,8 @@ Listing [[lst:bug-reference-mode]] configures ~bug-reference-mode~ for use with
 (ensure-package-installation 'debbugs)
 (defvar bug-reference-url-format
   "https://debbugs.gnu.org/cgi/bugreport.cgi?bug=%s"
-  "Setting this as a file local variable enables `bug-reference-mode'")
+  "Format to use `gnu-debbugs' URL.")
+(put 'bug-reference-mode 'safe-local-variable 'booleanp))
 #+end_src
 
 *** [[info:elisp#Debugging][Debugging Emacs Lisp (info)]]
@@ -5937,14 +5957,13 @@ point movements visually.
 #+begin_src emacs-lisp -n :results silent
 ;; https://karthinks.com/software/batteries-included-with-emacs/
 ;; https://github.com/karthink/.emacs.d/blob/master/init.el#L2077
-(require 'pulse) ; since `pulse' does not autoload `pulse-delay' and
-                 ; `pulse-iterations'.
-
 (defun flash-line-around-point (&rest _)
   "Flash the line around point."
-  (let ((pulse-iterations 16)
-        (pulse-delay 0.1))
-    (pulse-momentary-highlight-one-line (point))))
+  ;; BUG#71537: I cannot use `let' here without requiring `pulse', but
+  ;; `setq' has side effects.
+  (setq pulse-iterations 16
+        pulse-delay 0.1)
+  (pulse-momentary-highlight-one-line (point)))
 
 (dolist (command '(scroll-up-command
                    scroll-down-command
@@ -6403,7 +6422,7 @@ Only the [[info:org#Top][Org]] source file shows the local variables footer.
 # Emacs looks for "Local variables:" after the last "newline-formfeed".
 
 # Local Variables:
-# bug-reference-url-format: "https://debbugs.gnu.org/cgi/bugreport.cgi?bug=%s"
+# bug-reference-mode: t
 # compile-command: "latexmk -interaction=nonstopmode -lualatex -pvc -shell-escape README.tex"
 # fill-column: 80
 # org-edit-src-content-indentation: 0