bug#70949: display-buffer-choose-some-window

[Juri Linkov]

> And it will set up the '...-previous-window' variable

Not a variable, but a window parameter.  A buffer-local variable
can't be used because for example 'vc-diff-internal' uses such
call sequence:

  (set-buffer buffer)
  (pop-to-buffer (current-buffer))

so 'display-buffer' is called from 'pop-to-buffer' in the wrong buffer.

Therefore, when using a window parameter, the solution is very simple
like in the following patch that allows a short customization:

  (setq display-buffer-base-action
        '(nil (set-previous-window . t)))

Then users can use anything such as 'C-x 4 1' or 'C-x 4 4',
and after this the subsequent navigation will reuse
the same window.

Even 'next-error-no-select' ('n' and 'p' keys in the grep buffer)
that hard-codes 'inhibit-same-window', still uses the mru window,
because it's 'second-best-window'.

diff --git a/lisp/window.el b/lisp/window.el
index b014be6a7cf..ff12a2225b5 100644
--- a/lisp/window.el
+++ b/lisp/window.el
@@ -7883,7 +7888,8 @@ display-buffer
 specified by the ACTION argument."
   (interactive (list (read-buffer "Display buffer: " (other-buffer))
                     (if current-prefix-arg t)))
-  (let ((buffer (if (bufferp buffer-or-name)
+  (let ((old-selected-window (selected-window))
+        (buffer (if (bufferp buffer-or-name)
                    buffer-or-name
                  (get-buffer buffer-or-name)))
         (buf-name (if (bufferp buffer-or-name)
@@ -7933,6 +7938,8 @@ display-buffer
                         (select-window old-selected-window)))
                     (remove-hook 'post-command-hook postfun))))
           (add-hook 'post-command-hook postfun)))
+      (when (cdr (assq 'set-previous-window alist))
+        (set-window-parameter old-selected-window 'previous-window window))
       (and (windowp window) window))))
 
 (defun display-buffer-other-frame (buffer)
@@ -8638,6 +8645,7 @@ display-buffer-in-previous-window
                  (display-buffer-reuse-frames 0)
                  (t (last-nonminibuffer-frame))))
          (previous-window (cdr (assq 'previous-window alist)))
+         (set-previous-window (cdr (assq 'set-previous-window alist)))
         best-window second-best-window window)
     ;; Scan windows whether they have shown the buffer recently.
     (catch 'best
@@ -8654,6 +8662,9 @@ display-buffer-in-previous-window
     (when (and previous-window (symbolp previous-window)
                (boundp previous-window))
       (setq previous-window (symbol-value previous-window)))
+    (when-let ((set-previous-window)
+               (prev (window-parameter (selected-window) 'previous-window)))
+      (setq previous-window prev))
     (when (and (setq window previous-window)
               (window-live-p window)
               (or (eq buffer (window-buffer window))