Avoid GitHub queries for immutable references

[zanieb]

per #12746 (comment) it looks like we're not doing this as intended. This may require some investigation.

[charliermarsh]

I can take a look.

[charliermarsh]

Ah ok, I see the problem here.

[sbidoul]

I confirm the issue is resolved.

Issue opened in the evening, fixed when you wake up 😍

[charliermarsh]

Thank you for filing, it was a really good catch (and my mistake)!