Document the :language setting

Author: alco

lib/mix/lib/mix/project.ex

@@ -11,7 +11,7 @@ defmodule Mix.Project do
 
         def project do
           [app: :my_app,
-           vsn: "0.6.0"]
+           version: "0.6.0"]
         end
       end
 
@@ -24,6 +24,16 @@ defmodule Mix.Project do
   function in the project, the developer can call `Mix.Project.get!/0`
   which fails with `Mix.NoProjectError` in case a project is not
   defined.
+
+  ## Erlang projects
+
+  Mix can be used to manage Erlang projects that don't have any Elixir code. To
+  ensure mix tasks work correctly for an Erlang project, `language: :erlang`
+  has to be added to `project`.
+
+  The setting also makes sure Elixir is not added as a dependency to the
+  generated .app file or to the escript generated with `mix escript.build`,
+  etc.
   """
 
   @doc false

lib/mix/lib/mix/tasks/escript.build.ex

@@ -56,6 +56,13 @@ defmodule Mix.Tasks.Escript.Build do
     * `:emu_args` - emulator arguments to embed in the escript file.
       Defaults to `""`.
 
+  There is one project-level option that affects how the escript is generated:
+
+    * `language: :elixir | :erlang` - set it to `:erlang` for Erlang projects
+      managed by mix. Doing so will ensure Elixir is not embedded by default.
+      Your app will still be started as part of escript loading, with the
+      config used during build.
+
   ## Example
 
       defmodule MyApp.Mixfile do