Kubernetes kustomize operations in jsonnet

This repo contains kustomize.libsonnet - a jsonnet library that re-implements the core transformation operations of the Kubernetes kustomize tool.

There are two major differences from the real kustomize tool:

• The "overlay" file is described in jsonnet syntax, rather than kustomize.yaml. Jsonnet is significantly more powerful, so you can trivially implement (and share) new transformations using this approach.
• The file I/O directives of kustomize are not implemented. Jsonnet is a sand-boxed language, which is good for security, and a library cannot implement "new" ways to read files. kubecfg already supports importing content from YAML/JSON files, and from remote URLs.

See example.jsonnet for one way to apply these transformations to existing YAML manifest files. The example uses the kubecfg tool (to parse the input YAML files), although kustomize.libsonnet itself should also work in other jsonnet environments. It can also be combined with other jsonnet libraries, such as kube.libsonnet and k.libsonnet.

Note that (just like regular kustomize) projects using kustomize.libsonnet can "stack": Team A can import some upstream JSON/YAML (or jsonnet!) manifests, and apply a kustomize.libsonnet "overlay" to modify it for their particular needs. Team B can import the kustomize.libsonnet from team A and then apply another kustomize.libsonnet overlay with their additional needs, and so on.