emacs: Fix the References header in reply

In the new reply code, the References header gets inserted by
message.el using a function called message-shorten-references. Unlike
all the other header-inserting functions, it doesn't put a newline
after the header, causing the next header to end up on the same
line. In our case, this header happened to be User-Agent, so it's hard
to notice. This is probably a bug in message.el, but we need to work
around it.

This fixes the problem by wrapping message-shorten-references in a
function that inserts a newline after if necessary. This should
protect against the message.el bug being fixed in the future.

emacs/notmuch-mua.el

@@ -90,6 +90,15 @@ list."
 	else if (notmuch-match-content-type (plist-get part :content-type) "text/*")
 	  collect part))
 
+;; There is a bug in emacs 23's message.el that results in a newline
+;; not being inserted after the References header, so the next header
+;; is concatenated to the end of it. This function fixes the problem,
+;; while guarding against the possibility that some current or future
+;; version of emacs has the bug fixed.
+(defun notmuch-mua-insert-references (original-func header references)
+  (funcall original-func header references)
+  (unless (bolp) (insert "\n")))
+
 (defun notmuch-mua-reply (query-string &optional sender reply-all)
   (let ((args '("reply" "--format=json"))
 	reply
@@ -125,9 +134,22 @@ list."
 	  ;; Overlay the composition window on that being used to read
 	  ;; the original message.
 	  ((same-window-regexps '("\\*mail .*")))
+
+	;; We modify message-header-format-alist to get around a bug in message.el.
+	;; See the comment above on notmuch-mua-insert-references.
+	(let ((message-header-format-alist
+	       (loop for pair in message-header-format-alist
+		     if (eq (car pair) 'References)
+		     collect (cons 'References
+				   (apply-partially
+				    'notmuch-mua-insert-references
+				    (cdr pair)))
+		     else
+		     collect pair)))
 	  (notmuch-mua-mail (plist-get reply-headers :To)
 			    (plist-get reply-headers :Subject)
-			  (notmuch-headers-plist-to-alist reply-headers)))
+			    (notmuch-headers-plist-to-alist reply-headers))))
+
       ;; Insert the message body - but put it in front of the signature
       ;; if one is present
       (goto-char (point-max))

test/emacs

@@ -267,7 +267,6 @@ EOF
 test_expect_equal_file OUTPUT EXPECTED
 
 test_begin_subtest "Reply within emacs"
-test_subtest_known_broken
 test_emacs '(let ((message-hidden-headers ''()))
 	    (notmuch-search "subject:\"testing message sent via SMTP\"")
 	    (notmuch-test-wait)
@@ -292,7 +291,6 @@ EOF
 test_expect_equal_file OUTPUT EXPECTED
 
 test_begin_subtest "Reply from alternate address within emacs"
-test_subtest_known_broken
 add_message '[from]="Sender <sender@example.com>"' \
 	     [to]=test_suite_other@notmuchmail.org
 
@@ -318,7 +316,6 @@ EOF
 test_expect_equal_file OUTPUT EXPECTED
 
 test_begin_subtest "Reply from address in named group list within emacs"
-test_subtest_known_broken
 add_message '[from]="Sender <sender@example.com>"' \
             '[to]=group:test_suite@notmuchmail.org,someone@example.com\;' \
              [cc]=test_suite_other@notmuchmail.org
@@ -345,7 +342,6 @@ EOF
 test_expect_equal_file OUTPUT EXPECTED
 
 test_begin_subtest "Reply within emacs to a multipart/mixed message"
-test_subtest_known_broken
 test_emacs '(let ((message-hidden-headers ''()))
 	    (notmuch-show "id:20091118002059.067214ed@hikari")
 		(notmuch-show-reply)
@@ -409,7 +405,6 @@ EOF
 test_expect_equal_file OUTPUT EXPECTED
 
 test_begin_subtest "Reply within emacs to a multipart/alternative message"
-test_subtest_known_broken
 test_emacs '(let ((message-hidden-headers ''()))
 	    (notmuch-show "id:cf0c4d610911171136h1713aa59w9cf9aa31f052ad0a@mail.gmail.com")
 		(notmuch-show-reply)
@@ -450,7 +445,6 @@ EOF
 test_expect_equal_file OUTPUT EXPECTED
 
 test_begin_subtest "Quote MML tags in reply"
-test_subtest_known_broken
 message_id='test-emacs-mml-quoting@message.id'
 add_message [id]="$message_id" \
 	    "[subject]='$test_subtest_name'" \