Misleading Dependency proxy image prefix shown in the GitLab UI

Summary

When accessing the Dependency Proxy page in a group, it shows that the Dependency proxy image prefix is:

example.gitlab.com/groups/GROUP_NAME/dependency_proxy/containers

However, /groups/ should not be included. It should have been:

example.gitlab.com/GROUP_NAME/dependency_proxy/containers

If you tried to pull an image using example.gitlab.com/groups/GROUP_NAME/dependency_proxy/containers/alpine:latest it will fail with a 404 error.

Our documentation also states that the right prefix is example.gitlab.com/GROUP_NAME/dependency_proxy/containers.

Steps to reproduce

Enable Dependency Proxy.
Create a new group.
Access the group's Packages & Registries -> Dependency Proxy.

Example Group

https://gitlab.com/groups/codeclimate-dep-proxy-test

What is the current bug behavior?

Dependency proxy image prefix shown in the GitLab UI is wrong. For my example group, it's listed as:

gitlab.com/groups/codeclimate-dep-proxy-test/dependency_proxy/containers

What is the expected correct behavior?

It should have been listed as:

gitlab.com/codeclimate-dep-proxy-test/dependency_proxy/containers

Relevant logs and/or screenshots

Output of checks

This bug happens on GitLab.com

Results of GitLab environment info

Expand for output related to GitLab environment info


(For installations with omnibus-gitlab package run and paste the output of:
`sudo gitlab-rake gitlab:env:info`)

(For installations from source run and paste the output of:
`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`)

Results of GitLab application Check

Expand for output related to the GitLab application check

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)
(we will only investigate if the tests are passing)