anchor.diff:  
   FROM ubuntu:xenial as base_os_context
   
  +ENV DOCKER_VERSION=5:19.03.2~3-0~ubuntu-xenial
  +ENV CONTAINERD_VERSION=1.2.6-3
  +ENV OUTDIR=/out
  +
   # required for binary tools: ca-certificates, gcc, libc-dev, git, iptables, libltdl7
   # required for general build: make, wget, curl
   # required for ruby: libcurl4-openssl-dev
   # required for python: python3, pkg-config
   # hadolint ignore=DL3008
   RUN apt-get update && apt-get install -y --no-install-recommends \
  +    apt-transport-https \
       ca-certificates \
       curl \
  +    gnupg-agent \
  +    software-properties-common \
  +    ca-certificates \
       gcc \
       git \
       iptables \
  
positive.code: ADD https://storage.googleapis.com/kubernetes-release/release/v${KUBECTL_VERSION}/bin/linux/amd64/kubectl ${OUTDIR}/usr/bin/kubectl
  RUN chmod 555 ${OUTDIR}/usr/bin/kubectl
  
  # Docker
  RUN curl -fsSL https://download.docker.com/linux/ubuntu/gpg >/tmp/dkey
  RUN apt-key add /tmp/dkey
  RUN add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu xenial stable"
  RUN apt-get update && apt-get -qqy install --no-install-recommends docker-ce="${DOCKER_VERSION}~ubuntu"
  RUN mv /usr/bin/docker ${OUTDIR}/usr/bin
  
  # Cleanup stuff we don't need in the final image
  RUN rm -fr /usr/local/go/doc
  RUN rm -fr /usr/local/go/test
  
negative.code: ENV PROTOTOOL_VERSION=7df3b957ffe3d09dc57fe4e1eb96694614db8c7a
  ENV SHELLCHECK_VERSION=v0.7.0
  ENV UPX_VERSION=3.95
  ENV KIND_VERSION=v0.5.1
  
  WORKDIR /tmp
  