I'm considering dropping this entirely since dfpre:, dfpost:
dfn:, and s: can be just as powerful, if not more. patchid: is
inaccurate if either non-standard diff generation options are
used (e.g. -W or -U6); or if a MUAs mangle whitespace.
We'll keep patchid: at the top search input box for now, but the
textarea at the bottom (and possibly another textarea for a more
exact match) is probably more useful and flexible.