You can clone with
HTTPS or Subversion.
which sounds not conform to http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.26 :
if any of the entity tags match the entity tag of the entity that would have been returned in the response to a similar GET request (without the If-None-Match header) on that resource, or if "*" is given and any current entity exists for that resource, then the server MUST NOT perform the requested method, unless required to do so because the resource's modification date fails to match that supplied in an If-Modified-Since header field in the request.
This is a Werkzeug issue https://github.com/mitsuhiko/werkzeug/