[DRAFT PATCH] emacs: show local date next to Date: in case value differs

From: Tomi Ollila <t...@iki.fi>

When adding Date: header of a message to notmuch-show buffer, compare the
date string with local representation of it and if these differ, output
Date: {original-date-string}  ({local-date-representation})

This is useful e.g. when mail system provides Date: strings with
different timezone information than the sender is located at.

---
 emacs/notmuch-show.el | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/emacs/notmuch-show.el b/emacs/notmuch-show.el
index f15f981..7e81859 100644
--- a/emacs/notmuch-show.el
+++ b/emacs/notmuch-show.el
@@ -460,15 +460,28 @@ (defun notmuch-show-insert-header (header header-value)
   "Insert a single header."
   (insert header ": " (notmuch-sanitize header-value) "\n"))

-(defun notmuch-show-insert-headers (headers)
+(defun notmuch--make-date (timestamp)
+  (if (> timestamp 2147483647)
+      (message-make-date (seconds-to-time timestamp))
+    (message-make-date (encode-time timestamp 0 0 1 1 1970 t))))
+
+(defun notmuch-show-insert-headers (headers &optional timestamp)
   "Insert the headers of the current message."
-  (let ((start (point)))
+  (let ((start (point))
+       date-local)
     (mapc (lambda (header)
            (let* ((header-symbol (intern (concat ":" header)))
                   (header-value (plist-get headers header-symbol)))
-             (if (and header-value
-                      (not (string-equal "" header-value)))
-                 (notmuch-show-insert-header header header-value))))
+             (when (and header-value
+                        (not (string-equal "" header-value)))
+               (if (and timestamp
+                        (string-equal header "Date")
+                        (not (string-equal
+                              (setq date-local (notmuch--make-date timestamp))
+                              header-value)))
+                   (setq header-value
+                         (format "%s  (%s)" header-value date-local)))
+               (notmuch-show-insert-header header header-value))))
          notmuch-message-headers)
     (save-excursion
       (save-restriction
@@ -1012,7 +1025,7 @@ (defun notmuch-show-insert-msg (msg depth)
     ;; Set `headers-start' to point after the 'Subject:' header to be
     ;; compatible with the existing implementation. This just sets it
     ;; to after the first header.
-    (notmuch-show-insert-headers headers)
+    (notmuch-show-insert-headers headers (plist-get msg :timestamp))
     (save-excursion
       (goto-char content-start)
       ;; If the subject of this message is the same as that of the
-- 
1.9.1