anchor.diff:      gnupg2 \
       zip \
       software-properties-common
  +
   RUN curl -fsSL https://download.docker.com/linux/ubuntu/gpg | apt-key add -
   RUN add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/debian $(lsb_release -cs) stable"
   RUN apt-get update && \
  
positive.code: 
  # ci.xwiki.org expects:
  # - Java to be available at /home/hudsonagent/java8
  # - Maven to be available at /home/hudsonagent/maven
  RUN mkdir -p /home/hudsonagent && \
   ln -fs /root/.sdkman/candidates/java/current /home/hudsonagent/java8 && \
   ln -fs /home/hudsonagent/java8 /home/hudsonagent/java && \
   ln -fs /home/hudsonagent/java/bin/java /usr/bin/java && \
   ln -fs /root/apache-maven-3.6.0 /home/hudsonagent/maven && \
  
negative.code: 
  WORKDIR /root
  
  
  # Install the most recent version of Java8
  RUN apt-get -y upgrade openjdk-8-jdk openjdk-8-jre-headless
  
  # Add Zulu repository for Java7
  # Instructions from https://docs.azul.com/zulu/zuludocs/#ZuluUserGuide/PrepareZuluPlatform/AttachAPTRepositoryUbuntuOrDebianSys.htm
  # We're doing it at the beginning to avoid calling apt-get update several times.
  RUN apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 0xB1998361219BD9C9
  RUN echo 'deb http://repos.azulsystems.com/debian stable main' > /etc/apt/sources.list.d/zulu.list
  RUN apt-get update && apt-get -y install zulu-7
  
  # Copy VNC config files
  COPY vnc/.Xauthority .Xauthority
  