Feature: Ability to lookup a value from an outside file or current yaml document and use it within a format marker

[ahuffman]

This is a decent use case where I'd like to look something up with a query within the same file or an external file, and plug it's value into somewhere within a yaml file (terrible statement). This may be something better suited for pure templating, but I think this could reduce some of the needs for templating in general. This needs to be thought out more, but I wanted to capture the idea.

Example:

File 1 - To look up a value I'd like to use in my overlays

---
some:
  stuff:
     here: cool
other:
  stuff:
    here:
      a: apple
      b: banana

Instructions file feature usage

---
# "path" key optional and would lookup a reference in the original yaml document?
references:
  - name: ref1 
    path: ./file1.yaml
    query: some.stuff.here
  - name: ref2
    path: ./file2.yaml
    query: other.stuff.here[b]

yamlFiles:
  - path: /file/to/modify.yaml
    overlays:
      - name: Use ref1
        query: metadata.labels[app.kubernetes.io/name]
        value: "%r{ref1}"
        action: replace
      - name: Use ref2
        query: kind
        value: "%r{ref2}"
        action: replace

Expected Behavior:

1. overlay 1 replaces the value of metadata.labels['app.kubernetes.io/name'] with the value of cool
2. overlay 2 replaces the value of kind with the value banana

I'd like to use this to lookup and reference maps and arrays as well.

A use for this would be I deploy a bunch of stuff with Terraform and then spit it out in an orderly way with a template.

Then I want to populate a yaml based variables file with some of the info that I spit out from the terraform steps by looking up those references from the output to create a new yaml file that is properly configured for my new environment before further automation runs.

[ahuffman]

We do have the %v{r somefile.yaml}, but I want to look up (query) that file for the dynamic value's contents.