CI_CONFIG_PATH is unset when using a remote ci-configuration

thanks for allowing me to use a remote-file as a "Custom CI configuration path" (via the webinterface). That's a great (and long awaited) feature. I'm currently using it to run pipelines on immutable projects (where i maintain a fork of a git-repository, but really must not add a single file to the repo, to be able to track (and build) multiple branches of upstream with minimal effort).

Summary

When using a remote-file (hosted on a different server) as Custom CI configuration path (set via the webinterface), the CI_CONFIG_PATH as seen by the runners is empty.

Steps to reproduce

• Create a minimal gitlab-ci configuration file named my-ci.yml:

test:
  script:
    - echo "CI_CONFIG_PATH=${CI_CONFIG_PATH}"

• Upload this file onto a server, so it's available under something like https://example.com/my-ci.yml
• In your project, go to Settings->CI/CD->General Pipelines and set the Custom CI configuration path to the URL of your file (https://example.com/my-ci.yml)
• Trigger a run of the pipeline (manually, or push to the repository)

Example Project

https://gitlab.com/umlaeute/ci-test

What is the current bug behavior?

In the runner, the CI_CONFIG_PATH envvar is empty (or unset).

E.g. the above pipeline would generate the following output:

CI_CONFIG_PATH=

What is the expected correct behavior?

The runner should see the Custom CI configuration path as defined in the Project settings.

E.g. the above pipeline should generate the following output:

CI_CONFIG_PATH=https://example.com/my-ci.yml

Relevant logs and/or screenshots

Custom CI configuration path	expected CI_CONFIG_PATH	actual CI_CONFIG_PATH	example job
(empty)	.gitlab.yml	.gitlab.yml	https://gitlab.com/umlaeute/ci-test/-/jobs/403186384
.git-ci/gitlab.yml	.git-ci/gitlab.yml	.git-ci/gitlab.yml	https://gitlab.com/umlaeute/ci-test/-/jobs/403190799
https://gitlab.com/umlaeute/ci-test/raw/master/.git-ci/gitlab.yml	https://gitlab.com/umlaeute/ci-test/raw/master/.git-ci/gitlab.yml	(empty) 💥	https://gitlab.com/umlaeute/ci-test/-/jobs/403192300

Output of checks

This bug happens on GitLab.com, as well as my self-hosted Omnibus instance ( 12.6.4 (70900054dfe) )