fix: Use the right command to pull policies from oci registry

[gasparev]

Fixes #919

[jalseth]

Is this necessary? The CI attached to this PR works without the oci:// prefix.

[gasparev]

Is this necessary? The CI attached to this PR works without the oci:// prefix.

It's needed to pull from the GCP Artifact Registry at least

[jpreese]

When using push and pull the protocol doesn't have to be oci so it doesn't feel like putting it in the documentation is the right move. The protocol could also be https://, file://, etc.

What is an example from pulling from Google Artifact Registry? It may be an issue in how we are detecting the URL, e.g. https://github.com/open-policy-agent/conftest/blob/master/downloader/oci_detector.go#L31

[gasparev]

When using push and pull the protocol doesn't have to be oci so it doesn't feel like putting it in the documentation is the right move. The protocol could also be https://, file://, etc.

What is an example from pulling from Google Artifact Registry? It may be an issue in how we are detecting the URL, e.g. https://github.com/open-policy-agent/conftest/blob/master/downloader/oci_detector.go#L31

That explains the issue I see. Host names for Artifact Registry Docker hosts end in -docker.pkg.dev.

[jalseth]

Given this change is under an OCI heading in the docs, I'm OK with adding this if it means we aren't relying on regex for well-known artifact registries. Thanks for the PR!