Kapitan: Generic templated configuration management for Kubernetes, Terraform (kapitan.dev)

It's open sourced : https://github.com/kapicorp/kapitan maybe the sweet spot between helm , which is more a package manager for kubernetes applications; and kustomize which is a castrated and language specific but limited templating-engine , biggest limitation I've found is the lack of loop for files definition, and also is insufficient for everything that is not included by the language ( because it's very specific to kubernetes definition types )