Try running the shunit2 tests for the git step with bash

In GitHub Actions the tests using pushd/popd are failing which makes me wonder
/bin/sh in those environments is dash or something definitely not bash

stdlib/git/tests/simple.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 
 INVOCATION_FILE=$PWD/tmp_gittest_invocation_file.json