Use backward compatible command for current branch

Author: qgadrian

test/config/branch_test.exs renamed to test/config/branch_config_test.exs

@@ -1,11 +1,17 @@
-defmodule GitHooks.Config.BranchTest do
+defmodule GitHooks.Config.BranchConfigTest do
   @moduledoc false
 
   use ExUnit.Case, async: false
   use GitHooks.TestSupport.ConfigCase
 
   alias GitHooks.Config.BranchConfig
 
+  setup do
+    on_exit(fn ->
+      Application.delete_env(:git_hooks, :current_branch_fn)
+    end)
+  end
+
   describe "current_branch_allowed?/0" do
     test "when current branch is allowed to run for the git hook then current_branch_allowed? function returns true" do
       Application.put_env(:git_hooks, :current_branch_fn, fn -> {"master\n", 0} end)