     end
   end
 
+  # Determine the set of apps which have changed between two versions
   defp get_changed_apps(a, b) do
     as = Enum.map(a, fn app -> elem(app, 0) end) |> MapSet.new
     bs = Enum.map(b, fn app -> elem(app, 0) end) |> MapSet.new

    :ok
  end

  defp include_erts!(%Release{profile: %Profile{include_erts: false}}, _output_dir, _rel_dir), do: :ok
  defp include_erts!(%Release{profile: %Profile{include_erts: include_erts}} = release, output_dir, rel_dir) do
    prefix = case include_erts do
               true -> "#{:code.root_dir}"
               p when is_binary(p) -> Path.absname(p)

        {:error, "failed to strip release: #{inspect reason}"}
    end
  end
  defp strip_release(%Release{} = release), do: {:ok, release}
end
