anchor.diff:    buildNativeInputs = [bison]
       ++ stdenv.lib.optional (texinfo != null) texinfo
       ++ stdenv.lib.optional interactive readline;
  -   
  +
     postInstall = ''
       # Add an `sh' -> `bash' symlink.
       ln -s bash "$out/bin/sh"
   
  +  '' + (if interactive && bashCompletion != null then ''
  +    ensureDir "$out/etc"
  +    echo >"$out/etc/bash_completion" '. "${bashCompletion}/etc/bash_completion"'
  +  '' else ''
       # Install the completion examples.
       ensureDir "$out/etc"
       cp -v "examples/complete/bash_completion" "$out/etc"
   
       ensureDir "$out/etc/bash_completion.d"
       cp -v "examples/complete/complete.gnu-longopt" "$out/etc/bash_completion.d"
  -  '';
  +  '');
   
     meta = {
       homepage = http://www.gnu.org/software/bash/;
  
positive.code: {stdenv, fetchurl, readline ? null, interactive ? false, texinfo ? null, bison}:
  
  assert interactive -> readline != null;
  
  
negative.code: 
      license = "GPLv3+";
  
      maintainers = [ stdenv.lib.maintainers.ludo stdenv.lib.maintainers.simons ];
    };
  
    passthru = {
  