anchor.diff:  # PETPVC (https://github.com/UCL/PETPVC)
   #-------------------------------------------------------------------------------
   RUN \
  -    if [ ! -e  petpvc ]; then \
  +    if [ ! -e  $SOFT/petpvc ]; then \
           mkdir petpvc && \
           cd petpvc && \
           git clone https://github.com/UCL/PETPVC.git -b $PETPVC_VERSION && \
  
positive.code: # Camino (http://camino.cs.ucl.ac.uk/)
  #-------------------------------------------------------------------------------
  RUN \
      if [ ! -e  camino ]; then \
          git clone git://git.code.sf.net/p/camino/code camino \
      fi \
  
  
negative.code: # VTK (http://www.vtk.org)
  #-------------------------------------------------------------------------------
  RUN \
      if [ ! -e  $SOFT/vtk ]; then \
          mkdir vtk && \
          cd vtk && \
          git clone https://gitlab.kitware.com/vtk/vtk.git -b $VTK_VERSION VTK && \
  