If SHOW is non-nil, open the next item in a show
buffer. Otherwise just highlight the next item in the search
buffer. If PREVIOUS is non-nil, move to the previous item in the
-search results instead."
+search results instead.
+
+Return non-nil on success."
(interactive "P")
(let ((parent-buffer notmuch-show-parent-buffer))
(notmuch-bury-or-kill-this-buffer)