Maintain docker_tags.json
Maintain docker_tags.json

Getting tags from AWS ECR is unreliable. I've pushed images
whose tags show up in the ECR Repositories UI, but do not show up
in `aws ecr list-images --region us-east-1 --repository-name $REPO`.

This maintains a small file which can pushed around as a build artifact.

cookbrite/flyingcloud,cookbrite/flyingcloud