cli/reply: use decryption policy "auto" by default.

If the user doesn't specify --decrypt= at all, but a stashed session
key is known to notmuch, when replying to an encrypted message,
notmuch should just go ahead and decrypt.

The user can disable this at the command line with --decrypt=false,
though it's not clear why they would ever want to do that.

completion/notmuch-completion.bash

@@ -350,12 +350,16 @@ _notmuch_reply()
 	    COMPREPLY=( $( compgen -W "all sender" -- "${cur}" ) )
 	    return
 	    ;;
+	--decrypt)
+	    COMPREPLY=( $( compgen -W "true false" -- "${cur}" ) )
+	    return
+	    ;;
     esac
 
     ! $split &&
     case "${cur}" in
 	-*)
-	    local options="--format= --format-version= --reply-to= --decrypt ${_notmuch_shared_options}"
+	    local options="--format= --format-version= --reply-to= --decrypt= ${_notmuch_shared_options}"
 	    compopt -o nospace
 	    COMPREPLY=( $(compgen -W "$options" -- ${cur}) )
 	    ;;

doc/man1/notmuch-reply.rst

@@ -80,8 +80,12 @@ Supported options for **reply** include
         multipart/encrypted part will be replaced by the decrypted
         content.
 
+        If a session key is already known for the message, then it
+        will be decrypted automatically unless the user explicitly
+        sets ``--decrypt=false``.
+
         Decryption expects a functioning **gpg-agent(1)** to provide any
-        needed credentials. Without one, the decryption will fail.
+        needed credentials. Without one, the decryption will likely fail.
 
 See **notmuch-search-terms(7)** for details of the supported syntax for
 <search-terms>.

notmuch-reply.c

@@ -700,11 +700,12 @@ notmuch_reply_command (notmuch_config_t *config, int argc, char *argv[])
     int opt_index;
     notmuch_show_params_t params = {
 	.part = -1,
-	.crypto = { .decrypt = NOTMUCH_DECRYPT_FALSE },
+	.crypto = { .decrypt = NOTMUCH_DECRYPT_AUTO },
     };
     int format = FORMAT_DEFAULT;
     int reply_all = true;
     bool decrypt = false;
+    bool decrypt_set = false;
 
     notmuch_opt_desc_t options[] = {
 	{ .opt_keyword = &format, .name = "format", .keywords =
@@ -718,7 +719,7 @@ notmuch_reply_command (notmuch_config_t *config, int argc, char *argv[])
 	  (notmuch_keyword_t []){ { "all", true },
 				  { "sender", false },
 				  { 0, 0 } } },
-	{ .opt_bool = &decrypt, .name = "decrypt" },
+	{ .opt_bool = &decrypt, .name = "decrypt", .present = &decrypt_set },
 	{ .opt_inherit = notmuch_shared_options },
 	{ }
     };
@@ -728,8 +729,8 @@ notmuch_reply_command (notmuch_config_t *config, int argc, char *argv[])
 	return EXIT_FAILURE;
 
     notmuch_process_shared_options (argv[0]);
-    if (decrypt)
+    if (decrypt_set)
-	params.crypto.decrypt = NOTMUCH_DECRYPT_TRUE;
+	params.crypto.decrypt = decrypt ? NOTMUCH_DECRYPT_TRUE : NOTMUCH_DECRYPT_FALSE;
 
     notmuch_exit_if_unsupported_format ();
 

test/T357-index-decryption.sh

@@ -200,6 +200,16 @@ test_expect_equal \
     "$output" \
     "$expected"
 
+test_begin_subtest "notmuch reply should show cleartext if session key is present"
+output=$(notmuch reply id:simple-encrypted@crypto.notmuchmail.org | grep '^>')
+expected='> This is a top sekrit message.'
+if [ $NOTMUCH_HAVE_GMIME_SESSION_KEYS -eq 0 ]; then
+    test_subtest_known_broken
+fi
+test_expect_equal \
+    "$output" \
+    "$expected"
+
 
 # TODO: test removal of a message from the message store between
 # indexing and reindexing.