doom-kill-buffer: extract protect-visible-buffers logic

Protecting buffers that were visible in other windows (burying them
instead) is not the responsibility of doom-kill-buffer. This is a job
for kill-buffer-query-functions, hence doom|protect-visible-buffers.

core/autoload/buffers.el

@@ -179,11 +179,9 @@ DONT-SAVE is non-nil.
 See `doom-real-buffer-p' for what 'real' means."
   (setq buffer (or buffer (current-buffer)))
   (when (and (bufferp buffer) (buffer-live-p buffer))
-    (let ((buffer-win (get-buffer-window buffer))
-          (only-buffer-window-p (= 1 (length (get-buffer-window-list buffer nil t)))))
+    (let ((buffer-win (get-buffer-window buffer)))
       ;; deal with unsaved buffers
-      (when (and only-buffer-window-p
-                 (buffer-file-name buffer)
+      (when (and (buffer-file-name buffer)
                  (buffer-modified-p buffer))
         (with-current-buffer buffer
           (if (and (not dont-save)
@@ -201,10 +199,9 @@ See `doom-real-buffer-p' for what 'real' means."
               (doom--cycle-real-buffers -1)
               (when buffer-win
                 (unrecord-window-buffer buffer-win buffer))
-              (when only-buffer-window-p
-                (kill-buffer buffer)))
-            (not (eq (current-buffer) buffer)))
-        (kill-buffer buffer)))))
+              (kill-buffer buffer)))
+        (kill-buffer buffer)))
+    (not (eq (current-buffer) buffer))))
 
 ;;;###autoload
 (defun doom-force-kill-buffer (&optional buffer dont-save)

core/core-ui.el

@@ -228,6 +228,12 @@ local value, whether or not it's permanent-local. Therefore, we cycle
 (add-hook! '(doom-post-init-hook minibuffer-setup-hook)
   #'doom|no-fringes-in-minibuffer)
 
+(defun doom|protect-visible-buffers ()
+  "Don't kill the current buffer if it is visible in another window (bury it
+instead)."
+  (not (and after-init-time (get-buffer-window-list nil t))))
+(add-hook 'kill-buffer-query-functions #'doom|protect-visible-buffers)
+
 
 ;;
 ;; Plugins