Ensure registry garbage collection deletes blobs

Summary

I'm building three docker images with CI continuously via DinD. This should net 600 MB of images totally since all of them only have the latest tag (there should be only 1 image for all of these 3 The blobs in gitlab-rails/shared/registry/docker/registry/v2/blobs currently take up 12 GB.

I ran the garbage collection via sudo -u registry -H /opt/gitlab/embedded/bin/registry garbage-collect /var/opt/gitlab/registry/config.yml but it didn't delete anything. What else can I do about this?

Expected behavior

Most of the blobs should've been deleted.

Actual behaviour

Nothing was deleted.