Deleting image without tag

[odoucet]

Description

Hello,

We setup a docker registry several years ago (june 2016). The registry has grown, despite launching garbage-collect regularly.
After several hours of search, I found that some containers have no more tags but still exists :

curl -k https://registry.example/v2/myimage/tags/list
{"name":"myimage","tags":null}

but there are still many blobs referenced by this image :

bin/garbage-collect |grep myimage 
myimage : marking blob sha256:6df02cd4a5e421225aa96cf1be299a9f0e3d22154376442e7505f42b7d38149f
myimage : marking blob sha256:9f5d97e8c9ccd84eaf3b27bf1681b6f69edbafd4de3f7c65cdb50ab3490db67e
[...]

=> 104504 blobs counted!

when checking filesystem directly :

/data/docker/registry/v2/repositories/myimage/_manifest/tags: 0 file
/data/docker/registry/v2/repositories/myimage/_manifest/revisions/sha256/: 8725 files

is this related to #3851 ?

What can I do to completely remove myimage ?

Reproduce

1. launch registry
2. upload many images+tags
3. delete some tags
4. run garbage-collect
5. and do it over and over again

when deleting all tags for a specific image, the image must disappear

Expected behavior

No response

registry version

bin/registry github.com/docker/distribution 2.8.3

Additional Info

No response

[deleteriousEffect]

@odoucet are you using the -m flag when you run garbage collect?