Add 👏 Comments 👏 Explaining 👏 Unobvious 👏 Cache 👏 Behavior

[mcdonnnj]

🚀 Feature Proposal

A clear and concise description of what the feature is.

Motivation

Please outline the motivation for the proposal.

Example

Please provide an example for how this feature would be used.

Pitch

Why does this feature belong in this project?

[felddy]

@mcdonnnj Can you elaborate on this issue please.

[mcdonnnj]

@mcdonnnj Can you elaborate on this issue please.

Whoops. I never came back and fleshed this out.

[felddy]

https://github.com/docker/build-push-action/blob/master/docs/advanced/cache.md