This is an extract from the dfengine 1.05 source code.
2009-03-07 (Cyril Gantin)

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Integration of libcurl for requesting maps from an online repository.

Usage: /download <mapname>

Cvar dl_source defines the url from which to query maps, eg: http://someserver/somescript.php?q=%m
The %m token is replaced with the actual map name in the query.

The server MUST return an appropriate content-type. Accepted content-type values are either application/zip
or application/octet-stream. Other content-type values will be treated as errors or queries that didn't
yield results.

The server MAY return a content-disposition header with the actual name of the pk3 file. In the absence
of a content-disposition header, the client will write the pack to a default <mapname>.pk3 location. The
filename MUST have a pk3 extension. The filename MUST NOT have directory path information - slashes (/),
backslashes (\) and colons (:) are not accepted. Finally the filename MUST consist of us-ascii characters
only (chars 32 to 126, included). A filename that doesn't comply to these specifications will raise an
error and abort the transfer.

The server MAY redirect the query to another url. Multiple redirections are permitted - limit depends on
libcurl's default settings. The end query MUST return a "200 OK" http status code.

It is desirable that the server returns a content-length header with the size of the pk3 file.

The server MAY return a custom x-dfengine-motd header. Its value is a string that MUST NOT exceed 127
chars. The x-dfengine-motd string will be displayed after the download is complete. This is the place
where you take credits for setting up a server. :)

Downloaded files are written to the current gamedir of the home directory - eg. C:\quake3\mymod\ in
windows; ~/.q3a/mymod/ in linux. Name collision with an existing pk3 file will result in a failure and
be left to the user to sort out.

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