anchor.diff:  RUN \
       mkdir petpvc && \
       cd petpvc && \
  -    git clone https://github.com/UCL/PETPVC.git -b $PETPVC_VERSION && \
  +    git clone $PETPVC_GIT -b $PETPVC_VERSION && \
       mkdir build && \
       cd build && \
       cmake -DITK_DIR=$HOME/ants/build/ITKv4-build && \
  
positive.code: ENV WORKON_HOME $HOME/pyenvs
  
  RUN \
      echo "source /usr/local/bin/virtualenvwrapper.sh" >> $BASHRC && \
      echo "export WORKON_HOME=$HOME/pyenvs" >> $BASHRC && \
      echo "workon pytre" >> $BASHRC
  
negative.code: RUN \
      mkdir ants && \
      cd ants && \
      git clone $ANTS_GIT -b $ANTS_VERSION && \
      mkdir build && \
      cd build && \
      cmake -DUSE_VTK=ON \
  