Add OCI repository publish to ghcr.io for helm charts released from other repositories

[krajorama]

Followup to #2998 #2395

Implement releasing LGTM databases and other helm charts to github packages.
Update
https://github.com/grafana/helm-charts/blob/main/.github/workflows/update-helm-repo.yaml

[benoitschipper]

Hey All, I see there are already some Helm Charts being published as OCI Artifact (packages) here: https://github.com/orgs/grafana/packages?repo_name=helm-charts , or even within their own respective project within the grafana/*** github page.

I'd love to be able to also collect the following Helm Charts through GHCR as OCI Artifact:

• Loki - Helm Chart: https://github.com/grafana/loki/tree/main/production/helm/loki
• Mimir Distributed - Helm Chart: https://github.com/grafana/mimir
• Pyroscope - Helm Chart: https://github.com/grafana/pyroscope/tree/main/operations/pyroscope/helm/pyroscope
• Alloy - Helm Chart: https://github.com/grafana/alloy/tree/29baf3fd21a26e6004d9fef8221035db155b63db/operations/helm/charts/alloy
• Beyla - Helm Chart: https://github.com/grafana/beyla/tree/main/charts/beyla

The reason I like the OCI artifact has to do with the fact that I often require to work within airgapped environments. If the helm charts are available as OCI artifacts it allows me to gather and airgap these helm charts as OCI artifacts, the same way as I do with Images from multiple artifact repo's such as Docker/GHCR and more. Using tooling such as Skopeo Sync and Renovate to automatically alert me of a new version and decrease the amount of LCM.

Hope this makes sense! <3

[domolitom]

I have created a PR to add OCI publish to the workflow that is used by 'external' repositories (update-helm-repo):
#3366
@krajorama

[narqo]

For future references, to push an OCI package with a Helm chart from another repository, the helm-charts repo here needs explicitly give the permissions for original repository (e.g. grafana/mimir) to push a package. Refer to #3383 (comment) for details.

Refer to #3418 for better explanation of the problem.

[narqo]

Mimir Distributed - Helm Chart: https://github.com/grafana/mimir/tree/main/operations/helm/charts/mimir-distributed

Starting this weekly release, the mimir-distributed helm chart is pushed to the ghcr.io also. Check:

% gh auth token | helm registry login ghcr.io -u <user> --password-stdin

% helm template oci://ghcr.io/grafana/helm-charts/mimir-distributed --devel --version 5.6.0-weekly.316

It should also work for other charts that use the update-helm-repo.yaml workflow.