New variable 'use-short-answers' to use 'y-or-n-p' instead of 'yes-or-no-p'

* lisp/cus-start.el: Add use-short-answers.

* lisp/emacs-lisp/map-ynp.el (read-answer): Handle use-short-answers.
(read-answer-short): Add use-short-answers to docstring.

* src/fns.c (Fyes_or_no_p): Call y-or-n-p if use_short_answers is true.
(syms_of_fns): Add DEFVAR_BOOL use-short-answers (bug#46594).

etc/NEWS

@@ -2414,6 +2414,11 @@ and display the result.
 When non-nil, then functions 'read-char-choice' and 'y-or-n-p' (respectively)
 use the function 'read-key' to read a character instead of using the minibuffer.
 
+---
+** New variable 'use-short-answers' to use 'y-or-n-p' instead of 'yes-or-no-p'.
+This relieves of the need to define an alias that maps one to another
+in the init file.  The same variable also affects the function 'read-answer'.
+
 +++
 ** 'set-window-configuration' now takes an optional 'dont-set-frame'
 parameter which, when non-nil, instructs the function not to select

lisp/cus-start.el

@@ -302,6 +302,7 @@ Leaving \"Default\" unchecked is equivalent with specifying a default of
 	     ;; fns.c
 	     (use-dialog-box menu boolean "21.1")
 	     (use-file-dialog menu boolean "22.1")
+	     (use-short-answers menu boolean "28.1")
 	     (focus-follows-mouse
               frames (choice
                       (const :tag "Off (nil)" :value nil)

lisp/emacs-lisp/map-ynp.el

@@ -265,7 +265,8 @@ C-g to quit (cancel the whole command);
   "If non-nil, `read-answer' accepts single-character answers.
 If t, accept short (single key-press) answers to the question.
 If nil, require long answers.  If `auto', accept short answers if
-the function cell of `yes-or-no-p' is set to `y-or-n-p'."
+`use-short-answers' is non-nil, or the function cell of `yes-or-no-p'
+is set to `y-or-n-p'."
   :type '(choice (const :tag "Accept short answers" t)
                  (const :tag "Require long answer" nil)
                  (const :tag "Guess preference" auto))
@@ -304,7 +305,8 @@ Return a long answer even in case of accepting short ones.
 
 When `use-dialog-box' is t, pop up a dialog window to get user input."
   (let* ((short (if (eq read-answer-short 'auto)
-                    (eq (symbol-function 'yes-or-no-p) 'y-or-n-p)
+                    (or use-short-answers
+                        (eq (symbol-function 'yes-or-no-p) 'y-or-n-p))
                   read-answer-short))
          (answers-with-help
           (if (assoc "help" answers)

src/fns.c

@@ -2873,6 +2873,11 @@ if `last-nonmenu-event' is nil, and `use-dialog-box' is non-nil.  */)
       return obj;
     }
 
+  if (use_short_answers)
+    {
+      return call1 (intern ("y-or-n-p"), prompt);
+    }
+
   AUTO_STRING (yes_or_no, "(yes or no) ");
   prompt = CALLN (Fconcat, prompt, yes_or_no);
 
@@ -5904,6 +5909,15 @@ that disables the use of a file dialog, regardless of the value of
 this variable.  */);
   use_file_dialog = true;
 
+  DEFVAR_BOOL ("use-short-answers", use_short_answers,
+    doc: /* Non-nil means `yes-or-no-p' uses shorter answers "y" or "n".
+It's discouraged to use single-key answers because `yes-or-no-p' is
+intended to be used when it's thought that you should not respond too
+quickly, so you take time and perhaps think more about the answer.
+When non-nil, then `yes-or-no-p' uses `y-or-n-p' to read an answer.
+The same variable also affects the function `read-answer'.  */);
+  use_short_answers = false;
+
   defsubr (&Sidentity);
   defsubr (&Srandom);
   defsubr (&Slength);