emacs: Use pop-to-buffer-same-window rather than switch-to-buffer

This means that notmuch commands obey display-buffer-alist so the user
can customize how buffers show up.

It also permits the use of C-x 4 4, C-x 5 5 and C-x t t, available in
Emacs 28.  For example, one can use C-x 4 4 M-x notmuch-jump-search RET
to open a saved search in another window rather than the current window.
Or in notmuch-search mode, C-x 5 5 RET to view the message at point in
a new frame.

notmuch-tree has custom buffer display logic, so bind
display-buffer-overriding-action to make pop-to-buffer-same-window
behave exactly as switch-to-buffer while that function is running.

emacs/notmuch-draft.el

@@ -232,7 +232,8 @@ applied to newly inserted messages)."
 	 (draft (equal tags (notmuch-update-tags tags notmuch-draft-tags))))
     (when (or draft
 	      (yes-or-no-p "Message does not appear to be a draft: edit as new? "))
-      (switch-to-buffer (get-buffer-create (concat "*notmuch-draft-" id "*")))
+      (pop-to-buffer-same-window
+       (get-buffer-create (concat "*notmuch-draft-" id "*")))
       (setq buffer-read-only nil)
       (erase-buffer)
       (let ((coding-system-for-read 'no-conversion))

emacs/notmuch-hello.el

@@ -973,7 +973,7 @@ following:
   (let ((notmuch-hello-auto-refresh nil))
     (if no-display
 	(set-buffer "*notmuch-hello*")
-      (switch-to-buffer "*notmuch-hello*")))
+      (pop-to-buffer-same-window "*notmuch-hello*")))
   ;; Install auto-refresh hook
   (when notmuch-hello-auto-refresh
     (add-hook 'window-configuration-change-hook

emacs/notmuch-show.el

@@ -1244,7 +1244,7 @@ matched."
 		    (eval (car (get 'mm-inline-override-types 'standard-value))))
 	     (cons "application/*" mm-inline-override-types)
 	   mm-inline-override-types)))
-    (switch-to-buffer (get-buffer-create buffer-name))
+    (pop-to-buffer-same-window (get-buffer-create buffer-name))
     ;; No need to track undo information for this buffer.
     (setq buffer-undo-list t)
     (notmuch-show-mode)
@@ -2001,7 +2001,7 @@ to show, nil otherwise."
   (let* ((id (notmuch-show-get-message-id))
 	 (buf (get-buffer-create (concat "*notmuch-raw-" id "*")))
 	 (inhibit-read-only t))
-    (switch-to-buffer buf)
+    (pop-to-buffer-same-window buf)
     (erase-buffer)
     (let ((coding-system-for-read 'no-conversion))
       (call-process notmuch-command nil t nil "show" "--format=raw" id))
@@ -2060,7 +2060,7 @@ message."
 	  (set-buffer-modified-p nil)
 	  (setq buffer-read-only t)
 	  (unless (zerop exit-code)
-	    (switch-to-buffer-other-window buf)
+	    (pop-to-buffer buf)
 	    (message (format "Command '%s' exited abnormally with code %d"
 			     shell-command exit-code))))))))
 
@@ -2468,7 +2468,7 @@ If the part is displayed in an external application then close
 the new buffer."
   (let ((buf (get-buffer-create (generate-new-buffer-name
 				 (concat " *notmuch-internal-part*")))))
-    (switch-to-buffer buf)
+    (pop-to-buffer-same-window buf)
     (if (eq (mm-display-part handle) 'external)
 	(kill-buffer buf)
       (goto-char (point-min))

emacs/notmuch-tree.el

@@ -552,9 +552,14 @@ NOT change the database."
       (setq notmuch-tree-message-window
 	    (split-window-vertically (/ (window-height) 4)))
       (with-selected-window notmuch-tree-message-window
-	;; Since we are only displaying one message do not indent.
-	(let ((notmuch-show-indent-messages-width 0)
-	      (notmuch-show-only-matching-messages t))
+	(let (;; Since we are only displaying one message do not indent.
+	      (notmuch-show-indent-messages-width 0)
+	      (notmuch-show-only-matching-messages t)
+	      ;; Ensure that `pop-to-buffer-same-window' uses the
+	      ;; window we want it to use.
+	      (display-buffer-overriding-action
+		 '((display-buffer-same-window)
+		   (inhibit-same-window . nil))))
 	  (setq buffer (notmuch-show id))))
       ;; We need the `let' as notmuch-tree-message-window is buffer local.
       (let ((window notmuch-tree-message-window))
@@ -1119,7 +1124,7 @@ The arguments are:
 						(if unthreaded "unthreaded-" "tree-")
 						query "*")))))
 	(inhibit-read-only t))
-    (switch-to-buffer buffer))
+    (pop-to-buffer-same-window buffer))
   ;; Don't track undo information for this buffer
   (set 'buffer-undo-list t)
   (notmuch-tree-worker query query-context target open-target unthreaded)

emacs/notmuch.el

@@ -994,7 +994,7 @@ the configured default sort order."
 	 (buffer (get-buffer-create (notmuch-search-buffer-title query))))
     (if no-display
 	(set-buffer buffer)
-      (switch-to-buffer buffer))
+      (pop-to-buffer-same-window buffer))
     ;; avoid wiping out third party buffer-local variables in the case
     ;; where we're just refreshing or changing the sort order of an
     ;; existing search results buffer
@@ -1134,7 +1134,7 @@ notmuch buffers exist, run `notmuch'."
 	;; If the first one we found is any other than the starting
 	;; buffer, switch to it.
 	(unless (eq first start)
-	  (switch-to-buffer first))
+	  (pop-to-buffer-same-window first))
       (notmuch))))
 
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