Let's say you have a set of websites using the same source code and you want to speed up their deployments. You will have a reference website, let's say with site name reference-image. You will first deploy reference-image with:
The other websites then need add a reference to this image:
openode set-config REFERENCE_WEBSITE_IMAGE reference-image
Then when you openode deploy with this config, you will reuse the image from reference-image website and so the build will be more efficient.