Structure and version hints file

[migmartri]

Currently, the hints file format is a flat list of images. That does not leave any room for additional metadata such as the version of the schema/templating mechanism used.

Having the possibility of indicating the version of the file format is important since it's likely this file format might evolve in the future

My proposal is to change the schema to

message hintsFile {
  string version = 1; // optional, we can assume for now that's v1
  repeated string images = 2  
}

In practice this means that images need to be inside a :images property

So a hints file would go from

- "{{ .image.registry }}/{{ .image.repository }}:{{ .image.tag }}"
- "{{ .metrics.image.registry }}/{{ .metrics.image.repository }}:{{ .metrics.image.tag }}"
- "{{ .volumePermissions.image.registry }}/{{ .volumePermissions.image.repository }}:{{ .volumePermissions.image.tag }}"

to

images:
  - "{{ .image.registry }}/{{ .image.repository }}:{{ .image.tag }}"
  - "{{ .metrics.image.registry }}/{{ .metrics.image.repository }}:{{ .metrics.image.tag }}"
  - "{{ .volumePermissions.image.registry }}/{{ .volumePermissions.image.repository }}:{{ .volumePermissions.image.tag }}"

The implementation of the new format should be retro-compatible with the current one.

What do you think?

cc/ @tompizmor @josvazg @petewall

[petewall]

This is a good idea.

[josvazg]

LGTM