[PATCH v4 3/4] emacs: Tag forwarded messages with +forwarded (customizable)

["Örjan Ekeberg" <ekeberg@kth.se>]

Use the buffer-local variable notmuch-message-queued-tag-changes
to change tags when the forwarding message is sent.
---
 emacs/notmuch-message.el | 13 +++++++++++++
 emacs/notmuch-mua.el     | 14 ++++++++++++--
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/emacs/notmuch-message.el b/emacs/notmuch-message.el
index 0d4a8eee..0164472f 100644
--- a/emacs/notmuch-message.el
+++ b/emacs/notmuch-message.el
@@ -37,6 +37,19 @@ the \"inbox\" and \"todo\" tags, you would set:
   :type '(repeat string)
   :group 'notmuch-send)
 
+(defcustom notmuch-message-forwarded-tags '("+forwarded")
+  "List of tag changes to apply to a message when it has been forwarded.
+
+Tags starting with \"+\" (or not starting with either \"+\" or
+\"-\") in the list will be added, and tags starting with \"-\"
+will be removed from the message being forwarded.
+
+For example, if you wanted to add a \"forwarded\" tag and remove
+the \"inbox\" tag, you would set:
+    (\"+forwarded\" \"-inbox\")"
+  :type '(repeat string)
+  :group 'notmuch-send)
+
 (defconst notmuch-message-queued-tag-changes nil
   "List of messages and corresponding tag-changes to be applied when sending a message.
 
diff --git a/emacs/notmuch-mua.el b/emacs/notmuch-mua.el
index 2f0de92c..94fa19d7 100644
--- a/emacs/notmuch-mua.el
+++ b/emacs/notmuch-mua.el
@@ -478,7 +478,8 @@ the From: address."
 	    (list (cons 'From (notmuch-mua-prompt-for-sender)))))
 	 forward-subject  ;; Comes from the first message and is
 			  ;; applied later.
-	 forward-references) ;; List of accumulated message-references of forwarded messages
+	 forward-references ;; List of accumulated message-references of forwarded messages
+	 forward-queries) ;; List of corresponding message-query
 
     ;; Generate the template for the outgoing message.
     (notmuch-mua-mail nil "" other-headers nil (notmuch-mua-get-switch-function))
@@ -497,7 +498,8 @@ the From: address."
 		  ;; always generate a forwarded subject, then use the
 		  ;; last (i.e. first) one.
 		  (setq forward-subject (message-make-forward-subject))
-		  (push (message-fetch-field "Message-ID") forward-references))
+		  (push (message-fetch-field "Message-ID") forward-references)
+		  (push id forward-queries))
 		;; Make a copy ready to be forwarded in the
 		;; composition buffer.
 		(message-forward-make-body temp-buffer)
@@ -516,6 +518,14 @@ the From: address."
 	(message-add-header (concat "References: "
 				    (mapconcat 'identity forward-references " "))))
 
+      ;; Create a buffer-local queue for tag changes triggered when sending the message
+      (when notmuch-message-forwarded-tags
+	(setq-local notmuch-message-queued-tag-changes
+		    (loop for id in forward-queries
+			  collect
+			  (cons id
+				notmuch-message-forwarded-tags))))
+
       ;; `message-forward-make-body' shows the User-agent header.  Hide
       ;; it again.
       (message-hide-headers)
-- 
2.20.1