Seems to be back up. I assume they waived the rate limit.

    curl --head https://raw.github.com/git/git/master/Documentation/RelNotes/1.8.0.txt
    HTTP/1.1 200 OK
    Server: nginx
    Date: Mon, 22 Oct 2012 05:32:02 GMT
    Content-Type: text/plain; charset=utf-8
    Connection: keep-alive
    Status: 200 OK
    X-Runtime: 14
    X-RateLimit-Limit: 100
    Content-Length: 1
    X-Frame-Options: deny
    Cache-Control: no-cache
    X-RateLimit-Remaining: 100