-By default only those messages that match the search terms will be
-displayed. With this option, all messages in the same thread as any
-matched message will be displayed.
+If true,
+.B notmuch show
+outputs all messages in the thread of any message matching the search
+terms; if false, it outputs only the matching messages. For
+.B --format=json
+this defaults to true. For other formats, this defaults to false.