Added comment

Author: Nyholm

runtime/layers/function/bootstrap

@@ -7,6 +7,7 @@ set -e
 if [[ -z "${APP_RUNTIME}" ]]; then
   BOOTSTRAP="/opt/bref/bootstrap.php"
 else
+  # Split _HANDLER on ":" and take the first part
   BOOTSTRAP=(${_HANDLER//:/ })
 fi