It works for me, but it has the odd side-effect of prefixing links with a space. Fortunately that doesn't seem to break browsers.
And I'm sure someone else could come up with something better and more general.
+
+--[[KathrynAndersen]]
+
+> The `<base href>` is required to be genuinely absolute (HTML 4.01 ยง12.4).
+> Have you tried setting `url` to the public-facing URL, i.e. with `alfred`
+> as the hostname? That seems like the cleanest solution to me; if you're
+> one of the few behind the firewall and you access the site via `betty`
+> directly, my HTTP vs. HTTPS cleanup in recent versions should mean that
+> you rarely get redirected to `alfred`, because most URLs are either
+> relative or "local" (start with '/'). --[[smcv]]
+
+>> I did try setting `url` to the "Alfred" machine, but that doesn't seem clean to me at all, since it forces someone to go to Alfred when they started off on Betty.
+>> Even worse, it prevents me from setting up a test environment on, say, Cassandra, because as soon as one tries to search, one goes to Alfred, then Betty, and not back to Cassandra at all.
+>> Hardcoded solutions make me nervous.
+
+>> I suppose what I would like would be to not need to use a `<base href>` in searching at all.
+>> --[[KathrynAndersen]]
+
+>>> `<base href>` is *not* required to be absolute in HTML5, so when
+>>> `html5: 1` is used, I've changed it to be host-relative in most cases.
+>>> I think that at least partially addresses this bug report,
+>>> particularly if we [[todo/generate HTML5 by default]] like I've suggested.
+>>>
+>>> The `<base>` is there so we can avoid having to compute how to
+>>> get to (the virtual directory containing) the root of the wiki from
+>>> `ikiwiki.cgi`, which might well be somewhere odd like `/cgi-bin/`.
+>>> I think there are probably other things that it fixes or simplifies.
+>>> --[[smcv]]