[Feature-Request] RegexManager Checksum-Download Support

[Preisschild]

What would you like Renovate to be able to do?

I use a regexmanager (with github-releases datasource) to update versions of tooling inside Dockerfiles. in the end it looks like this:

# renovate: datasource=github-releases depName=GoogleContainerTools/skaffold
ARG SKAFFOLD_VERSION=v1.16.0
ARG SKAFFOLD_CHECKSUM=9041feb75a5fc15c1159f1e25d0dd781ecf0ff9fe37190174e61822a47c60b1d

With the RegexManager looking like this.

"regexManagers": [
    {
      "fileMatch": ["(^|/|\\.)Dockerfile$", "(^|/)Dockerfile\\.[^/]*$"],
      "matchStrings": [
        "# renovate: datasource=(?<datasource>[a-z-]+?) depName=(?<depName>.+?)(?: versioning=(?<versioning>[a-z-0-9]+?))?\\s(?:ENV|ARG) .+?_VERSION=(?<currentValue>.+?)\\s"
      ],
      "versioningTemplate": "{{#if versioning}}{{versioning}}{{else}}semver{{/if}}"
    }
]

This works great for updating the Version, but it would also be cool if Renovate could update the Checksum (in this example ARG SKAFFOLD_CHECKSUM).

Did you already have any implementation ideas?
We could add a capture group that captures checksumUrl and another one that captures currentChecksumValue. This signals to renovate that it should update the checksum by downloading checksumUrl and passing the body.

Edit: We'd also need to allow inserting the new version into the url

[Preisschild]

@HonkingGoose I think the manager got mislabeled. I mean the regexmanager.

[HonkingGoose]

We don't have a RegEx manager label yet, so I thought this seems to apply to Dockerfiles, I'll stick a manager:dockerfile label on it.

I'll remove the manager:dockerfile label. 😄