bug#33992: 27.0.50; xref-find-definitions wastes too much space

[Felician Nemeth]

(Sorry for replying late, I've just read this bug report.)

I thought that I didn't need to see the list of the xref results and the
xrefs' window shrank the view of the code I wanted to study.  So, I came
up with the defun below.  It presents the xref results without showing
the xref window.  I think this idea can be further developed.
xref-show--xrefs-buffer could have an 'm' key binding that "minimizes"
its window by switching to xref-show-xrefs-without-buffer (below) and
that function can "maximize" back with the same 'm' key.  A customizable
variable could define the initial behavior.

Also, I think we can enhance xref-pulse-momentarily to use a different
face if there's only one xref to present.

(defun xref-show-xrefs-without-buffer (xrefs alist)
  "Present the results of an xref query in a simple manner.
To activate this feature, customize `xref-show-xrefs-function'."
  (xref--show-xref-buffer xrefs alist)
  (quit-window)
  (next-error)
  (message "%s (%s xrefs in total)"
           "\",\": previous xref \".\":next xref \"m\":show xref buffer"
           (length xrefs))
  (set-transient-map
   (let ((map (make-sparse-keymap)))
     (define-key map (kbd ",") 'previous-error)
     (define-key map (kbd ".") 'next-error)
     (define-key map (kbd "m")
       (lambda () (interactive) (pop-to-buffer xref-buffer-name)))
     map)
   t))
(setq xref-show-xrefs-function 'xref-show-xrefs-without-buffer)