anchor.diff:  
   # jenkins version being bundled in this docker image
   ARG JENKINS_VERSION
  -ENV JENKINS_VERSION ${JENKINS_VERSION:-2.32.3}
  +ENV JENKINS_VERSION ${JENKINS_VERSION:-2.73.2}
   
   # jenkins.war checksum, download will be validated using it
  -ARG JENKINS_SHA=a25b9a314ca9e76f9673da7309e1882e32674223
  +ARG JENKINS_SHA=f6d1351beef34d980b32f8c463be505445f637e2fc62156fecd42891c53c97d3
   
   # Can be used to customize where jenkins.war get downloaded from
   ARG JENKINS_URL=https://repo.jenkins-ci.org/public/org/jenkins-ci/main/jenkins-war/${JENKINS_VERSION}/jenkins-war-${JENKINS_VERSION}.war
  
positive.code: RUN usermod -aG docker jenkins
  
  # Install Docker-Compose
  RUN curl -L "https://github.com/docker/compose/releases/download/1.10.0/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose
  RUN chmod +x /usr/local/bin/docker-compose
  
  
  
negative.code: # could use ADD but this one does not check Last-Modified header neither does it allow to control checksum 
  # see https://github.com/docker/docker/issues/8331
  RUN curl -fsSL ${JENKINS_URL} -o /usr/share/jenkins/jenkins.war \
    && echo "${JENKINS_SHA}  /usr/share/jenkins/jenkins.war" | sha256sum -c -
  
  ENV JENKINS_UC https://updates.jenkins.io
  RUN chown -R ${user} "$JENKINS_HOME" /usr/share/jenkins/ref
  