add forwarding call to generate config from nerves release template

lib/mix/tasks/nerves.release.init.ex

@@ -0,0 +1,18 @@
+defmodule Mix.Tasks.Nerves.Release.Init do
+  use Mix.Task
+
+  @moduledoc """
+  Prepares a new project for use with releases.
+  By default, this forwards the call to
+    mix release.init --template /path/to/nerves/release_template.eex
+
+  For more information on additional args, reference
+    mix help release.init
+  """
+
+  @spec run(OptionParser.argv) :: no_return
+  def run(args) do
+    template_path = Path.join(["#{:code.priv_dir(:nerves)}", "templates", "release.eex"])
+    Mix.Task.run("release.init", args ++ ["--template", template_path])
+  end
+end

priv/templates/release.eex

@@ -0,0 +1,54 @@
+use Mix.Releases.Config,
+    # This sets the default release built by `mix release`
+    default_release: :default,
+    # This sets the default environment used by `mix release`
+    default_environment: :dev
+<%= unless no_docs do %>
+# For a full list of config options for both releases
+# and environments, visit https://hexdocs.pm/distillery/configuration.html
+<% end %>
+<%= unless no_docs do %>
+# You may define one or more environments in this file,
+# an environment's settings will override those of a release
+# when building in that environment, this combination of release
+# and environment configuration is called a profile
+<% end %>
+environment :dev do
+  set cookie: <%= inspect(cookie) %>
+end
+
+environment :prod do
+  set cookie: <%= inspect(cookie) %>
+end
+<%= unless no_docs do %>
+# You may define one or more releases in this file.
+# If you have not set a default release, or selected one
+# when running `mix release`, the first release in the file
+# will be used by default<% end %>
+<%= for release <- releases do %><%= if Keyword.get(release, :is_umbrella) do %>
+release :<%= Keyword.get(release, :release_name) %> do
+  set version: "0.1.0"
+  set applications: [
+<%= Enum.map(Keyword.get(release, :release_applications), fn {app, start_type} ->
+    "    #{app}: :#{start_type}"
+    end) |> Enum.join(",\n") %>
+  ]
+  if System.get_env("NERVES_SYSTEM") do
+    set dev_mode: false
+    set include_src: false
+    set include_erts: System.get_env("ERL_LIB_DIR")
+    set include_system_libs: System.get_env("ERL_SYSTEM_LIB_DIR")
+    set vm_args: "rel/vm.args"
+  end
+end<% else %>
+release :<%= Keyword.get(release, :release_name) %> do
+  set version: current_version(:<%= Keyword.get(release, :release_name)%>)
+  if System.get_env("NERVES_SYSTEM") do
+    set dev_mode: false
+    set include_src: false
+    set include_erts: System.get_env("ERL_LIB_DIR")
+    set include_system_libs: System.get_env("ERL_SYSTEM_LIB_DIR")
+    set vm_args: "rel/vm.args"
+  end
+end<% end %>
+<% end %>