       #=> "/path/to/project/_build/dev"
 
   """
+  @spec build_path(Keyword.t) :: Path.t
   def build_path(config \\ config()) do
     config[:env_path] || env_path(config)
   end

  Use it only to configure aspects of your project (like
  compilation directories) and not your application runtime.
  """
  def config do
    case Mix.ProjectStack.peek do
      %{config: config} -> config

      #=> "/path/to/project/deps"

  """
  @spec deps_path(Keyword.t) :: Path.t
  def deps_path(config \\ config()) do
    Path.expand config[:deps_path]
  end
