Instead of returning a command which gets executed and which should
pass through / stream its output data to the client, we're just
returning an instance of Pluf_HTTP_Response. This is needed, because
some SCMs, most noticable monotone, have no locally executable command
to provide a snapshot archive (and probably never will for our kind
of setup).
We therefor added a little BSD-licensed class "ZipArchive" which allows
the creation of pkzip-compatible archives on the fly by letting it eat
the file contents directly feed from the (remote) stdio instance.
Download performance is ok and lies between 15K/s and 110K/s, but at
least we do no longer block the browser while we pre-generate the zip
file server-side.
Thanks to Patrick Georgi for all his work!
