Make minibuffer-eldef-shorten-default obsolete

* lisp/minibuf-eldef.el (minibuffer-eldef-shorten-default): Make
variable obsolete in favor of 'minibuffer-default-prompt-format'.
* doc/emacs/mini.texi (Basic Minibuffer): Delete above obsolete
variable (bug#50935).

doc/emacs/mini.texi

@@ -58,12 +58,8 @@ the default argument is shown with the user option
 Emacs hides the default argument as soon as you modify the contents of
 the minibuffer (since typing @key{RET} would no longer submit that
 default).  If you ever bring back the original minibuffer text, the
-prompt again shows the default.  Furthermore, if you change the
-variable @code{minibuffer-eldef-shorten-default} to a non-@code{nil}
-value, the default argument is displayed as @samp{[@var{default-arg}]}
-instead of @samp{(default @var{default-arg})}, saving some screen
-space.  To enable this minor mode, type @kbd{M-x
-minibuffer-electric-default-mode}.
+prompt again shows the default.  To enable this minor mode, type
+@kbd{M-x minibuffer-electric-default-mode}.
 
   Since the minibuffer appears in the echo area, it can conflict with
 other uses of the echo area.  If an error message or an informative

etc/NEWS

@@ -109,6 +109,12 @@ files when the Emacs session which locked it crashes, or was otherwise
 interrupted, and didn't exit gracefully.  See the "(emacs) Saving
 Emacs Sessions" node in the Emacs manual for more details.
 
+** Miscellaneous
+
++++
+*** User option 'minibuffer-eldef-shorten-default' is now obsolete.
+Customize the user option 'minibuffer-default-prompt-format' instead.
+
 
 * Startup Changes in Emacs 29.1
 

lisp/minibuf-eldef.el

@@ -64,6 +64,8 @@
   :type 'boolean
   :group 'minibuffer
   :version "24.3")
+(make-obsolete-variable 'minibuffer-eldef-shorten-default
+                        'minibuffer-default-prompt-format "29.1")
 
 (defvar minibuffer-default-in-prompt-regexps
   (minibuffer-default--in-prompt-regexps)