[docker] How to ignore ubuntu-20 updates if ubuntu-22 is available

[MarvinVaillant]

Hello everybody,

we use dependabot to keep our Dockerfiles up to date. Today I faced an interesting update suggestion that I'd like to ignore in the future.

Currently we have a dockerfile with a base image like this:

FROM summerwind/actions-runner:v2.319.1-ubuntu-22.04-1be410b

You see the version of the tool v2.319.1, then the base image they used ubuntu-22.04 and a hash. Given this dockerfile Dependabot suggested to update to v2.321.0-ubuntu-20.04-xxxxxx (please note the ubuntu version downgraded to 20.04). Even though there is also a variant with for ubuntu 22.04 (v2.321.0-ubuntu-22.04-xxxxxx).

Do you know how I can ignore any ubuntu-20.04 dependabot updates in the future?

When using wildcards dependabot complains about invalid syntax:

...
    ignore:
      - dependency-name: 'summerwind/actions-runner'
        versions: '*-ubuntu-20.04-*'
...