Enforcing clone/fetch to use references.

[resending with corrected subject]

Suppose I want to publish some changes to a tree. I have a server available where I can run a git daemon, but for one reason or another I want to force people to use the another git repo as a reference. The reason could be one of bandwidth, or someone who isn't comfortable making all of the other source available. Ideally, someone who already has the other git repo cloned, and just adds mine as a remote wouldn't notice the difference.

Is there a way to do this? I've tried various ways of using alternates to keep the blobs out of the repository I want to export, but the daemon just follows the alternates. If I remove the alternates, I then seem to have a broken repository. Most things I try, at least carry objects for all of the files in the HEAD tree, which most of the time is a large portion of the data.

If there isn't a way of doing this currently, is this something that others would find useful?

Thanks, David