message-toggle-gcc

[Emilio Lopes]

Despite its name, it also needs Gnus.  I bind it to "C-c C-f C-g"
in `message-mode-map'.

(defun message-toggle-gcc ()
  "Insert or remove the \"Gcc\" header."
  (interactive)
  (save-excursion
    (save-restriction
      (message-narrow-to-headers)
      (if (message-fetch-field "Gcc")
          (message-remove-header "Gcc")
        (gnus-inews-insert-archive-gcc)))))