anchor.diff:            -L "$melpa/package-build" \
             -l "$melpa2nix" \
             -f melpa2nix-build-package \
  -          $pname $version
  +          $ename $version
   
         runHook postBuild
       '';
  
positive.code:   preUnpack = ''
      mkdir -p "$NIX_BUILD_TOP/recipes"
      if [ -n "$recipe" ]; then
        cp "$recipe" "$NIX_BUILD_TOP/recipes/$pname"
      fi
  
      ln -s "$melpa/package-build" "$NIX_BUILD_TOP/package-build"
  
negative.code:   installPhase = ''
      runHook preInstall
  
      archive="$NIX_BUILD_TOP/packages/$ename-$version.el"
      if [ ! -f "$archive" ]; then
          archive="$NIX_BUILD_TOP/packages/$ename-$version.tar"
      fi
  
      emacs --batch -Q \
  