From: Stefan Monnier <monnier@iro.umontreal.ca>
Date: Tue, 25 Mar 2025 15:23:48 +0000 (-0400)
Subject: lisp/gnus/mm-encode.el (mm-default-buffer-type): Obey the mode hierarchy
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=c8adfab7effeb2ee9ff82132140458eb63d19334;p=emacs.git

lisp/gnus/mm-encode.el (mm-default-buffer-type): Obey the mode hierarchy

(cherry picked from commit e67f03bf35b97d2898b64281215be6717b659839)
---

diff --git a/lisp/gnus/mm-encode.el b/lisp/gnus/mm-encode.el
index 021c56e26ef..ef75b6da6e1 100644
--- a/lisp/gnus/mm-encode.el
+++ b/lisp/gnus/mm-encode.el
@@ -110,7 +110,8 @@ This variable should never be set directly, but bound before a call to
 (defun mm-default-buffer-type (buffer)
   "Return a default content type for BUFFER, a buffer name."
   (if-let* ((buf (get-buffer buffer))
-            ((eq (buffer-local-value 'major-mode buf) 'diff-mode)))
+            ((provided-mode-derived-p (buffer-local-value 'major-mode buf)
+                                      'diff-mode)))
       "text/x-patch" "text/plain"))
 
 (defun mm-safer-encoding (encoding &optional type)