Convert checkout to a regular action (#70)

__test__/verify-basic.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+if [ ! -f "./basic/basic-file.txt" ]; then
+    echo "Expected basic file does not exist"
+    exit 1
+fi
+
+# Verify auth token
+cd basic
+git fetch