docker.pkg.github.com support?

It seems, that the image is uploaded, but then an error happens on trying to pull the image. Context is below.

My pipeline config is something like this:

resources:
# ...
- name: docker-registry
  type: docker-image
  source:
    repository: docker.pkg.github.com/it-projects-llc/hound/pr
    username: ((github-username))
    password: ((github-token))

jobs:
# ....
  - put: docker-registry
    params:
      build: pr
      dockerfile: pr/DockerfilePR
      tag_file: pr-info/tag.txt

When I try to pull locally, the command does not work:

$ docker pull docker.pkg.github.com/it-projects-llc/hound/pr@sha256:4c836c350d9f38061f96428228bd26f672afca7c6e3f48d486101bc45783af49
Error response from daemon: manifest for docker.pkg.github.com/it-projects-llc/hound/pr@sha256:4c836c350d9f38061f96428228bd26f672afca7c6e3f48d486101bc45783af49 not found

But it does works with the tag. And you can see that the downloaded tag has the same sha:

$ docker pull docker.pkg.github.com/it-projects-llc/hound/pr:pr-8-head-e520d7f-base-33f8705 
pr-8-head-e520d7f-base-33f8705: Pulling from it-projects-llc/hound/pr
89d9c30c1d48: Already exists 
7196c122958a: Already exists 
c374e3dd66a7: Already exists 
585ea8360d37: Already exists 
10e1bd8c3dd3: Already exists 
6e0205926582: Already exists 
56d962d43dca: Pull complete 
0aa135f6d7bb: Pull complete 
Digest: sha256:4c836c350d9f38061f96428228bd26f672afca7c6e3f48d486101bc45783af49
Status: Downloaded newer image for docker.pkg.github.com/it-projects-llc/hound/pr:pr-8-head-e520d7f-base-33f8705

Start by reproducing the Concourse pipeline configuration and the two docker pull commands shown in the issue, comparing digest-based and tag-based pulls from docker.pkg.github.com. Trace the docker-image resource's registry interaction until the digest lookup is understood; done means the shown image can be pulled by digest as well as by tag, with coverage for the reported behavior.