bug#59862: quit-restore per window buffer

bug#59862: quit-restore per window buffer

[Juri Linkov]

1. C-x 4 d RET C-h C-t q q         -- the bottom window is NOT deleted
2. C-x 4 d RET C-h C-t C-x k RET q -- the bottom window is deleted
3. C-x 4 d RET C-h C-n C-x k RET q -- the bottom window is NOT deleted

The accidental difference between the last two is that the former uses
`switch-to-buffer' whereas the latter uses `pop-to-buffer-same-window'.

The root of the problem is that displaying a buffer in an existing
window, or quitting a buffer in an existing window overwrites its
window parameter `quit-restore', and thus invalidates the history of
how the first window was displayed.

A partial fix that solves only the first test case above is at least
not to overwrite `quit-restore' on quitting other buffers in the same
window:

```
diff --git a/lisp/window.el b/lisp/window.el
index a11293d372a..e3b057599d5 100644
--- a/lisp/window.el
+++ b/lisp/window.el
@@ -5275,14 +5276,14 @@ quit-restore-window
 	(set-window-prev-buffers
 	 window (append (window-prev-buffers window) (list entry))))
       ;; Reset the quit-restore parameter.
-      (set-window-parameter window 'quit-restore nil)
       ;; Select old window.
       ;; If the previously selected window is still alive, select it.
       (window--quit-restore-select-window quit-restore-2))
      (t
       ;; Show some other buffer in WINDOW and reset the quit-restore
       ;; parameter.
-      (set-window-parameter window 'quit-restore nil)
       ;; Make sure that WINDOW is no more dedicated.
       (set-window-dedicated-p window nil)
       ;; Try to switch to a previous buffer.  Delete the window only if
```

But the proper fix for other problems would be to replace the window
parameter `quit-restore' currently shared by all buffers in the same window
by a stack where every window buffer should keep own quit-restore data.
There is already such a stack in `window-prev-buffers', so a possible
solution would be to add quit-restore data to each buffer
in window-prev-buffers.

Alternatively, it would be nice to have an option that would prevent
overwriting the initial value of the window parameter `quit-restore',
thus `quit-restore-window' could delete the window regardless of
how many buffers were displayed in that window, like it does in case
of dedicated windows.