USE_CURL_MULTI and http.h in general

The changes I made to the commit-walker fetch code turn out not to work with USE_CURL_MULTI, and I'm not at all clear on how to deal with it. I think the current code for USE_CURL_MULTI also can't work for having multiple things in the same executable using http.h, which will be a problem for having both ls-remote and http-fetch as part of builtin-fetch, as well as eventually calling http-push without an exec from builtin-push. Is there anyone around who understands it?

	-Daniel
*This .sig left intentionally blank*