mu4e: added action to show the current thread only

Add an action for view and headers buffer to show only the messages in
the current thread.

mu4e/mu4e-actions.el

@@ -268,6 +268,16 @@ store your org-contacts."
 
     (mu4e-message (concat "tagging: " (mapconcat 'identity taglist ", ")))
     (mu4e-refresh-message path maildir)))
+
+(defun mu4e-action-show-thread (msg)
+  "Show all messages that are in the same thread as the message
+at point."
+  (let ((msgid (mu4e-message-field msg :message-id)))
+    (when msgid
+      (let ((mu4e-headers-show-threads t)
+	     (mu4e-headers-include-related t))
+        (mu4e-headers-search
+         (format "msgid:%s" msgid))))))
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 

mu4e/mu4e-headers.el

@@ -194,7 +194,8 @@ Field must be a symbol, one of: :date, :subject, :size, :prio,
 
 
 (defvar mu4e-headers-actions
-  '( ("capture message" . mu4e-action-capture-message))
+  '( ("capture message"  . mu4e-action-capture-message) 
+     ("show this thread" . mu4e-action-show-thread))
   "List of actions to perform on messages in the headers list.
 The actions are of the form (NAME SHORTCUT FUNC) where:
 * NAME is the name of the action (e.g. \"Count lines\")

mu4e/mu4e-view.el

@@ -99,7 +99,8 @@ directory and saves all attachments in the chosen directory."
 
 (defvar mu4e-view-actions
   '( ("capture message"  . mu4e-action-capture-message)
-     ("view as pdf"     . mu4e-action-view-as-pdf))
+     ("view as pdf"      . mu4e-action-view-as-pdf)
+     ("show this thread" . mu4e-action-show-thread))
   "List of actions to perform on messages in view mode.
 The actions are of the form:
   (NAME FUNC)