github / gist caching issue

[Alex Efros]

When I update graph in gist image don't get updated unless I also change url (like rename document). According to github/markup#224 (comment) your service should also set one of Expires, Last-Modified or Etag headers.

[Hugo Freire Gil]

Thanks @powerman, I think we have already discuse this problem before in other issue and I have already added one of this tags. I will check it.