Add new ./apis directory and codegen scripts.

Signed-off-by: Matt Moyer <moyerm@vmware.com>

hack/lib/verify-codegen.sh

@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+
+# Copyright 2020 VMware, Inc.
+# SPDX-License-Identifier: Apache-2.0
+set -euo pipefail
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+KUBE_VERSIONS=("$@")
+
+GENERATED_DIR="${ROOT}/generated"
+BACKUP_DIR="${GENERATED_DIR}.bak"
+
+# Move the originally generated directory to a backup location
+mv "${GENERATED_DIR}" "${BACKUP_DIR}"
+mkdir "${GENERATED_DIR}"
+
+# At exit (even on error), copy it back
+cleanup() {
+    rm -r "${GENERATED_DIR}"
+    mv -f "${BACKUP_DIR}" "${GENERATED_DIR}"
+}
+trap "cleanup" EXIT SIGINT
+
+# Run the code generation into a new empty `./generated` directory.
+"${ROOT}/hack/lib/update-codegen.sh" "${KUBE_VERSIONS[@]}"
+
+# Diff each of the chosen Kubernetes versions (but avoid comparing any other versions).
+echo "diffing ${GENERATED_DIR} against freshly generated codegen"
+ret=0
+for kubeVersion in "${KUBE_VERSIONS[@]}"; do
+    kubeMinorVersion="$(echo "${kubeVersion}" | cut -d"." -f1-2)"
+    generatedVersionDir="${GENERATED_DIR}/${kubeMinorVersion}"
+    backupVersionDir="${BACKUP_DIR}/${kubeMinorVersion}"
+    diff -Naupr "${generatedVersionDir}" "${backupVersionDir}" || ret=$?
+done
+
+# If any of the versions differed, exit nonzero with an error message.
+if [[ $ret -eq 0 ]]
+then
+  echo "${GENERATED_DIR} up to date."
+else
+  echo "${GENERATED_DIR} is out of date. Please run hack/update.sh"
+  exit 1
+fi