Add a U binding to switch to unthreaded from other views

We have shortcuts S and Z to let the user switch to Search view and
Tree view with the current search. Add U to let the user switch to
unthreaded view from the current search, and ensure that S and Z
switch from unthreaded to search and tree veiew respectively.

emacs/notmuch-show.el

@@ -50,6 +50,8 @@
 (declare-function notmuch-tree "notmuch-tree"
 		  (&optional query query-context target buffer-name open-target unthreaded))
 (declare-function notmuch-tree-get-message-properties "notmuch-tree" nil)
+(declare-function notmuch-unthreaded
+		  (&optional query query-context target buffer-name open-target))
 (declare-function notmuch-read-query "notmuch" (prompt))
 (declare-function notmuch-draft-resume "notmuch-draft" (id))
 
@@ -1471,6 +1473,7 @@ reset based on the original query."
   (let ((map (make-sparse-keymap)))
     (set-keymap-parent map notmuch-common-keymap)
     (define-key map "Z" 'notmuch-tree-from-show-current-query)
+    (define-key map "U" 'notmuch-unthreaded-from-show-current-query)
     (define-key map (kbd "<C-tab>") 'widget-backward)
     (define-key map (kbd "M-TAB") 'notmuch-show-previous-button)
     (define-key map (kbd "<backtab>") 'notmuch-show-previous-button)
@@ -1559,6 +1562,13 @@ All currently available key bindings:
 		notmuch-show-query-context
 		(notmuch-show-get-message-id)))
 
+(defun notmuch-unthreaded-from-show-current-query ()
+  "Call notmuch unthreaded with the current query"
+  (interactive)
+  (notmuch-unthreaded notmuch-show-thread-id
+		      notmuch-show-query-context
+		      (notmuch-show-get-message-id)))
+
 (defun notmuch-show-move-to-message-top ()
   (goto-char (notmuch-show-message-top)))
 

emacs/notmuch-tree.el

@@ -294,6 +294,8 @@ FUNC."
     (define-key map [remap notmuch-jump-search] (notmuch-tree-close-message-pane-and #'notmuch-jump-search))
 
     (define-key map "S" 'notmuch-search-from-tree-current-query)
+    (define-key map "U" 'notmuch-unthreaded-from-tree-current-query)
+    (define-key map "Z" 'notmuch-tree-from-unthreaded-current-query)
 
     ;; these use notmuch-show functions directly
     (define-key map "|" 'notmuch-show-pipe-message)
@@ -474,6 +476,18 @@ NOT change the database."
     (notmuch-tree-close-message-window)
     (notmuch-tree query)))
 
+(defun notmuch-unthreaded-from-tree-current-query ()
+  "Switch from tree view to unthreaded view"
+  (interactive)
+  (unless notmuch-tree-unthreaded
+    (notmuch-tree-refresh-view 'unthreaded)))
+
+(defun notmuch-tree-from-unthreaded-current-query ()
+  "Switch from unthreaded view to tree view"
+  (interactive)
+  (when notmuch-tree-unthreaded
+    (notmuch-tree-refresh-view 'tree)))
+
 (defun notmuch-search-from-tree-current-query ()
   "Call notmuch search with the current query"
   (interactive)
@@ -635,19 +649,24 @@ message will be \"unarchived\", i.e. the tag changes in
   (when (window-live-p notmuch-tree-message-window)
     (notmuch-tree-show-message-in)))
 
-(defun notmuch-tree-refresh-view ()
+(defun notmuch-tree-refresh-view (&optional view)
   "Refresh view."
   (interactive)
   (when (get-buffer-process (current-buffer))
     (error "notmuch tree process already running for current buffer"))
   (let ((inhibit-read-only t)
 	(basic-query notmuch-tree-basic-query)
+	(unthreaded (cond ((eq view 'unthreaded) t)
+			  ((eq view 'tree) nil)
+			  (t notmuch-tree-unthreaded)))
 	(query-context notmuch-tree-query-context)
 	(target (notmuch-tree-get-message-id)))
     (erase-buffer)
     (notmuch-tree-worker basic-query
 			 query-context
-			 target)))
+			 target
+			 nil
+			 unthreaded)))
 
 (defun notmuch-tree-thread-top ()
   (when (notmuch-tree-get-message-properties)

emacs/notmuch.el

@@ -190,6 +190,7 @@ there will be called at other points of notmuch execution."
     (define-key map (kbd "RET") 'notmuch-search-show-thread)
     (define-key map (kbd "M-RET") 'notmuch-tree-from-search-thread)
     (define-key map "Z" 'notmuch-tree-from-search-current-query)
+    (define-key map "U" 'notmuch-unthreaded-from-search-current-query)
     map)
   "Keymap for \"notmuch search\" buffers.")
 (fset 'notmuch-search-mode-map notmuch-search-mode-map)
@@ -523,6 +524,11 @@ thread."
   (interactive)
   (notmuch-tree notmuch-search-query-string))
 
+(defun notmuch-unthreaded-from-search-current-query ()
+  "Call notmuch tree with the current query"
+  (interactive)
+  (notmuch-unthreaded notmuch-search-query-string))
+
 (defun notmuch-tree-from-search-thread ()
   "Show the selected thread with notmuch-tree"
   (interactive)