For security reasons, one of the sites I'm in charge of uses a Reverse Proxy to grab the content from another machine behind our firewall.
Let's call the out-facing machine Alfred and the one behind the firewall Betty.

For the static pages, everything is fine.  However, when trying to use the search, all the links break.
This is because, when Alfred passes the search query on to Betty, the search result has a "base" tag which points to Betty, and all the links to the "found" pages are relative.
So we have

    <base href="Betty.example.com"/>
    ...
    <a href="./path/to/found/page/">path/to/found/page</a>

This breaks things for anyone on Alfred, because Betty is behind a firewall and they can't get there.

What would be better is if it were possible to have a "base" which didn't reference the hostname, and for the "found" links not to be relative.
Something like this:

    <base href="/"/>
    ...
    <a href="/path/to/found/page/">path/to/found/page</a>

The workaround I've come up with is this.

1. Set the "url" in the config to '&nbsp;' (a single space).  It can't be empty because too many things complain if it is.
2. Patch the search plugin so that it saves an absolute URL rather than a relative one.

Here's a patch:

    diff --git a/IkiWiki/Plugin/search.pm b/IkiWiki/Plugin/search.pm
    index 3f0b7c9..26c4d46 100644
    --- a/IkiWiki/Plugin/search.pm
    +++ b/IkiWiki/Plugin/search.pm
    @@ -113,7 +113,7 @@ sub indexhtml (@) {
            }
            $sample=~s/\n/ /g;
    
    -       my $url=urlto($params{destpage}, "");
    +       my $url=urlto($params{destpage}, undef);
            if (defined $pagestate{$params{page}}{meta}{permalink}) {
                    $url=$pagestate{$params{page}}{meta}{permalink}
            }

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.