anchor.diff:            if [ "$name" = "dll.conf" ] || [ "$name" = "saned.conf" ] || [ "$name" = "net.conf" ]; then
               cat "$conf" >> "$out/etc/sane.d/$name"
             else
  -            ln -s "$conf" "$out/etc/sane.d/$name"
  +            symlink "$conf" "$out/etc/sane.d/$name"
             fi
           done
         fi
   
         if [ -e "${path}/etc/sane.d/dll.d" ]; then
           find "${path}/etc/sane.d/dll.d" -maxdepth 1 -not -type d | while read conf; do
  -          ln -s "$conf" "$out/etc/sane.d/dll.d/$(basename $conf)"
  +          symlink "$conf" "$out/etc/sane.d/dll.d/$(basename $conf)"
           done
         fi
       '';
  
positive.code: let installSanePath = path: ''
        if [ -e "${path}/lib/sane" ]; then
          find "${path}/lib/sane" -maxdepth 1 -not -type d | while read backend; do
            ln -s "$backend" "$out/lib/sane/$(basename "$backend")"
          done
        fi
  
  
negative.code:   phases = "installPhase";
  
    installPhase = ''
      function symlink () {
        local target=$1 linkname=$2
        if [ -e "$linkname" ]; then
          echo "warning: conflict for $linkname. Overriding."
        fi
        ln -sfn "$target" "$linkname"
      }
  
      mkdir -p $out/etc/sane.d $out/etc/sane.d/dll.d $out/lib/sane
    '' + concatMapStrings installSanePath paths;
  }
  