elixir-lang/elixir — pull request #2315 by chyndman (2014-05-21 22:01:33+00:00)
Title: Mix.CLITest: explicitly declare environment variables (Windows-friendly)

Bash shell commands happily allow prefixing environment variable assignments for temporary use (i.e. MY_ENV="my_value" my_command --my-args), but Windows shells don't support this. So, we need to use System.put_env/2 and System.delete_env/1 to mimic this behavior (which should also work in bash.