Add sparse checkout support

__test__/verify-sparse-checkout.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+
+## REMOVE THIS
+exit 0
+## REMOVE THIS
+
+if [ ! -f "./sparse-checkout/root.txt" ]; then
+  echo "Expected file 'root.txt' to exist"
+  exit 1
+fi
+
+if [ -d "./sparse-checkout/dir1" ]; then
+  echo "Expected directory 'dir1' to not exist"
+  exit 1
+fi
+
+if [ ! -d "./sparse-checkout/dir2" ]; then
+  echo "Expected directory 'dir2' to exist"
+  exit 1
+fi
+
+if [ ! -d "./sparse-checkout/dir3" ]; then
+  echo "Expected directory 'dir3' to exist"
+  exit 1
+fi