anchor.diff:    docbook_xsl_ns != null &&
     docbook_xsl != null &&
     (fop != null || !enableJava) &&
  -# TODO: Package this:
  -#  epubcheck != null &&
  +  epubcheck != null &&
     gnused != null &&
     coreutils != null;
   
  
positive.code: , docbook_xsl_ns ? null
  , docbook_xsl ? null
  , fop ? null
  # TODO: Package this:
  #, epubcheck ? null
  , gnused ? null
  , coreutils ? null
  
  
negative.code:         -e "s|twopi|${graphviz}/bin/twopi|g" \
          -e "s|circo|${graphviz}/bin/circo|g" \
          -e "s|fdp|${graphviz}/bin/fdp|g" \
          -i "asciidoc/resources/filters/graphviz/graphviz2png.py"
  
      sed -e "s|run('latex|run('${texlive}/bin/latex|g" \
          -e "s|cmd = 'dvipng'|cmd = '${texlive}/bin/dvipng'|g" \
          -e "s|cmd = 'dvisvgm'|cmd = '${texlive}/bin/dvisvgm'|g" \
          -i "asciidoc/resources/filters/latex/latex2img.py"
  
      sed -e "s|run('abc2ly|run('${lilypond}/bin/abc2ly|g" \
          -e "s|run('lilypond|run('${lilypond}/bin/lilypond|g" \
          -e "s|run('convert|run('${imagemagick.out}/bin/convert|g" \
          -i "asciidoc/resources/filters/music/music2png.py"
  
      sed -e 's|filter="source-highlight|filter="${sourceHighlight}/bin/source-highlight|' \
          -e 's|filter="highlight|filter="${highlight}/bin/highlight|' \
          -e 's|filter="pygmentize|filter="${pygments}/bin/pygmentize|' \
          -i "asciidoc/resources/filters/source/source-highlight-filter.conf"
  
      # ENV is custom environment passed to programs that a2x invokes. Here we
      # use it to work around an impurity in the tetex package; tetex tools
  