The edit page CGI defines a `base` tag with an URL which is not
absolute, which can break the preview function in some circumstances
(with e.g. images not showing). The trivial [[patch]] that fixes
it can be found [[here|http://sprunge.us/EPHT]] as well as on [[my
git|http://git.oblomov.eu/ikiwiki]].

> That patch does mean that if you're accessing the CGI via HTTPS but your
> $config{url} and $config{cgiurl} are HTTP, you'll get preview images loaded
> via HTTP, causing the browser to complain. See
> [[todo/want_to_avoid_ikiwiki_using_http_or_https_in_urls_to_allow_serving_both]]
> for background.
>
> Perhaps the CGI could form its `<base>` URL by using
> `URI->new_abs(urlto(...), $cgi->url)` instead?
>
> You'd also need to change `IkiWiki/Wrapper.pm` to pass at least the
> SERVER_NAME and SERVER_PORT through the environment, probably.
>
> Joey's last comment on
> [[todo/want_to_avoid_ikiwiki_using_http_or_https_in_urls_to_allow_serving_both]]
> suggests that this might already work, but I'm not quite sure how - I'd
> expect it to need more environment variables? --[[smcv]]
>
>> `CGI::url` uses `REQUEST_URI`. So it could be used, but I don't see
>> how to get from the `CGI::url` to an url to the page that is being
>> edited. --[[Joey]]