emacs: reply: remove wrong sig/enc status buttons

This stops the (usually incorrect) sigstatus and encstatus buttons
appearing when replying in emacs, and updates the test suite to match.

Overriding the status button functions is a little unusual but much
less intrusive than passing an argument all the way down the call
chain. It also makes it clear exactly what it does.

We also hide the application/pgp-encrypted part as it can only contain
"Version: 1". We do this in notmuch show, which means it also happens
when replying.

emacs/notmuch-mua.el

@@ -253,8 +253,11 @@ mutiple parts get a header."
 		       (notmuch-show-insert-header-p-function notmuch-mua-reply-insert-header-p-function)
 		       ;; Don't indent multipart sub-parts.
 		       (notmuch-show-indent-multipart nil))
-		    (notmuch-show-insert-body original (plist-get original :body) 0)
-		    (buffer-substring-no-properties (point-min) (point-max)))))
+		    ;; We don't want sigstatus buttons (an information leak and usually wrong anyway).
+		    (letf (((symbol-function 'notmuch-crypto-insert-sigstatus-button) #'ignore)
+			   ((symbol-function 'notmuch-crypto-insert-encstatus-button) #'ignore))
+			  (notmuch-show-insert-body original (plist-get original :body) 0)
+			  (buffer-substring-no-properties (point-min) (point-max))))))
 
 	(set-mark (point))
 	(goto-char start)

emacs/notmuch-show.el

@@ -682,6 +682,9 @@ will return nil if the CID is unknown or cannot be retrieved."
       (indent-rigidly start (point) 1)))
   t)
 
+(defun notmuch-show-insert-part-application/pgp-encrypted (msg part content-type nth depth button)
+  t)
+
 (defun notmuch-show-insert-part-multipart/* (msg part content-type nth depth button)
   (let ((inner-parts (plist-get part :content))
 	(start (point)))

test/T310-emacs.sh

@@ -384,8 +384,6 @@ References: <20091118002059.067214ed@hikari>
 --text follows this line--
 Adrian Perez de Castro <aperez@igalia.com> writes:
 
-> [ Unknown signature status ]
->
 > Hello to all,
 >
 > I have just heard about Not Much today in some random Linux-related news

test/T350-crypto.sh

@@ -317,7 +317,6 @@ test_expect_equal \
     "$expected"
 
 test_begin_subtest "Reply within emacs to an encrypted message"
-test_subtest_known_broken
 test_emacs "(let ((message-hidden-headers '())
       (notmuch-crypto-process-mime 't))
   (notmuch-show \"subject:test.encrypted.message.002\")