ytt (pronounced spelled out) is a templating tool that understands YAML
structure. It helps you easily configure complex software via reusable
templates and user provided values. Ytt includes the following features:

* Structural templating: understands yaml structure so users can focus on their
  configuration instead of issues associated with text templating, such as YAML
  value quoting or manual template indentation
* Built-in programming language: includes the "fully featured" Python-like
  programming language Starlark which helps ease the burden of configuring
  complex software through a richer set of functionality.
* Reusable configuration: You can reuse the same configuration in different
  environments by applying environment-specific values.
* Custom validations: coupled with the fast and deterministic execution, allows
  you to take advantage of faster feedback loops when creating and testing
  templates.
* Overlays: this advanced configuration helps users manage the customization
  required for complex software. For more, see this example in the online
  playground.
* Sandboxing: provides a secure, deterministic environment for execution of
  templates.