For issue #4235 ("Inform HTTP caching proxies regarding the delta base used in svndiff-style GET responses"), raise an error in the client if the server reports a delta base that differs from the one we requested.
For issue #4235 ("Inform HTTP caching proxies regarding the delta base
used in svndiff-style GET responses"), raise an error in the client if
the server reports a delta base that differs from the one we requested.

* subversion/libsvn_ra_serf/update.c
  (handle_fetch): Compare the X-SVN-VR-Base header value in the GET
    response with the one in the GET request.  If they differ, error
    out.  (But allow for the situation where the server failed to
    return the header at all, as will be true for pre-1.8 servers).


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1390685 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion