You can clone with
HTTPS or Subversion.
On the page/section: http://piwik.org/faq/how-to-install/#faq_98
For standard proxy, the default value presented are:
;proxy_client_headers = HTTP_X_FORWARDED_FOR
;proxy_host_headers = HTTP_X_FORWARDED_FOR
For proxy_host_headers the value should be HTTP_X_FORWARDED_HOST. For an inattentive reader it could be really painful to understand what is going on.
Thanks that's fixed!