v1.0.0-rc6 https://groups.google.com/a/opencontainers.org/d/msg/dev/CHg2TvPYnlQ/AR1IpDUjBgAJ https://github.com/opencontainers/image-spec/pull/681
v1.0.0-rc6 https://groups.google.com/a/opencontainers.org/d/msg/dev/CHg2TvPYnlQ/AR1IpDUjBgAJ https://github.com/opencontainers/image-spec/pull/681