Ecto flattened migrations, initial migration

initial_schema.exs

defmodule MyApp.Repo.Migrations.InitialSchema do
  use Ecto.Migration

  def up do
    db = Application.fetch_env!(:my_app, MyApp.Repo)
    file_path = "priv/repo/initial_schema.sql"

    {output, errno} =
      System.cmd(
        "psql",
        [
          "-f", file_path,
          "-U", db[:username],
          "-h", db[:hostname],
          db[:database]
        ],
        env: [{"PGPASSWORD", db[:password]}]
      )

    if errno != 0 do
      raise "psql error: #{output}"
    end
  end

  def down do
    raise "Rollback of initial schema not allowed"
  end
end