Add wrapper for YTT

.gitignore

@@ -6,3 +6,5 @@ obj/
 /.idea/
 /.vs/
 /.vscode/
+
+/tools/

tool.properties

@@ -0,0 +1,2 @@
+ytt_version=v0.36.0
+ytt_mirror=https://github.com/vmware-tanzu/carvel-ytt/releases/download

yttw.sh

@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+
+set -e
+
+# =========================================================================== #
+# wrapper for ytt                                                             #
+# =========================================================================== #
+
+base_dir=$(dirname $0)
+ytt=$base_dir/tools/ytt
+
+if [ ! -x $ytt ]; then
+  ytt_version=$(grep '^ytt_version=' $base_dir/tool.properties | cut -d= -f2)
+  ytt_mirror=$(grep '^ytt_mirror=' $base_dir/tool.properties | cut -d= -f2)
+  case $(uname -s) in
+    Darwin) platform=darwin ;;
+    Linux) platform=linux ;;
+    *)
+      echo "unsupported platform: $(uname -s)"
+      exit 1
+      ;;
+  esac
+  ytt_url=$ytt_mirror/$ytt_version/ytt-$platform-amd64
+  mkdir -p $(dirname $ytt)
+  wget $ytt_url -O $ytt
+  chmod +x $ytt
+fi
+
+exec $ytt $*