GCR Image Cleanup - list or delete all but the 5 newest tags for all images in a GCR repository

gcr_cleanup.sh

#!/usr/bin/env bash

# Exit if no arguments are passed
if [ $# -lt 1 ]; then
cat << HELP

gcr_cleanup  --  list or delete all but the 5 newest tags for all images

EXAMPLE: 
    - list all but the 5 newest tags for all images
       gcr_cleanup gcr.io/project-name

    - delete all but the 5 newest tags for all images
       FINAL_ANSWER=doittoit gcr_cleanup gcr.io/project-name

HELP
exit 0
fi

# List all images in the repo
images() {
  gcloud container images list --repository "$1" --format='value(name)'
}

# List all tags for an image, excluding the 5 newest
# If an image has 5 or less tags, this will return nothing
image_tags() {
  gcloud container images list-tags "$1" --format='value(tags)' --sort-by='~timestamp' | tail -n +6
}

# Prints the tags that need to be cleaned up
# Will delete them for you if you set the FINAL_ANSWER environment variable to "doittoit"
main() {
  for image in $(images "$1"); do
    for tag in $(image_tags "$image"); do
      IFS=','
      for innertag in $tag; do
        if [[ $FINAL_ANSWER == 'doittoit' ]]; then
          gcloud container images untag "$image:$innertag"
        else
          echo "$image:$innertag"
        fi
      done
      unset IFS
    done
  done
}

main "$@"