Chart.yaml

apiVersion: v1
name: blah
version: 1

manifest.yaml

value: {{ .Values.env_name }}

data:
  services:
    {{- range $key, $val := .Values.services }}
    {{ $key }}:
      branch: {{ $val.branch }}
    {{- end }}

run.sh

#!/bin/bash

helm template . -x templates/manifest.yaml --set services.api.branch=funny --set services.frontend.branch=something

values.yaml

services:
  app:
    branch: master

Need to move manifest.yaml into templates directory to get this to work because that is how helm works.