anchor.diff:    dontBuild = false;
     src = fetchurl { inherit url sha256; };
   
  -  buildInputs = lib.optional withLibvirt [ libvirt pkgconfig ];
  -
     patches = [
       ./unofficial-installation-nowarn.patch
       ./use-system-bundler-version.patch
  
positive.code: { lib, fetchurl, buildRubyGem, bundlerEnv, ruby, libarchive, writeText, withLibvirt ? true, libvirt, pkgconfig }:
  
  let
    # NOTE: bumping the version and updating the hash is insufficient;
  
negative.code:   postInstall = ''
      wrapProgram "$out/bin/vagrant" \
        --set GEM_PATH "${deps}/lib/ruby/gems/${ruby.version.libDir}" \
        --prefix PATH ':' "${lib.getBin libarchive}/bin"
  
      mkdir -p "$out/vagrant-plugins/plugins.d"
      echo '{}' > "$out/vagrant-plugins/plugins.json"
  