Feature Request: Regex pattern support for tag filtering/exclusion

[nicl-dev]

Starting with a discussion before I create an issue for this request to check if it's something that you would consider in scope for this project first.

I have an image that uses date-based development tags (e.g., kopia/kopia:20251116.0.63645) which Cup detects as major updates, even though they're just timestamped development builds rather than actual releases.

Currently, the only workaround (that I know of) is to exclude the entire image, but this means missing legitimate stable releases.

Proposed Solution:

Add regex pattern support for tag filtering in the exclusion configuration. For example:

{
  "images": {
    "exclude_tags": [
      "kopia/kopia:\\d{8}\\..*"
    ]
  }
}

This would allow excluding timestamp-based development tags while still monitoring for stable releases like latest or semantic versions.
Alternative Consideration:
If regex is too complex, perhaps a simpler tag pattern matching system (e.g., kopia/kopia:202* or kopia/kopia:..!([0-9]{8}.*)) could achieve similar results.

Edit: I just realized I probably should have created this as an idea. Apologies.

[sergi0g]

Yeah this is something I have been planning on doing, but practically requires a rewrite that would make things more flexible. Unfortunately, for now you'll have to exclude the image. Sorry!

[nicl-dev]

That was quick! :D And that's totally fine. It's cool that it's on the roadmap for some point in the future, thank you!

[danroc]

@sergi0g, this is not exactly what @nicl-dev suggested, but could the existing images.exclude config also apply to remote tags? Maybe get_latest_tag could ignore tags based on that config.

We could then add kopia/kopia:202 to the excluded images.

(I can open a PR if you are ok with this approach.)

[sergi0g]

@danroc if you mean using exclude's prefix-based matching on remote tags too, that's a great idea and should be default behavior! And yes, a PR would be lovely!

As an implementation note, you'll probably want to add a debug log that image X (or images X, Y, ..., depending on if you want to batch things which I think is a good idea) was excluded based on filter A where A is the exact value from exclude that caused the match. Keep in mind that a single image may have tags matching 2 or more filters (continuing your Kopia example, a user may have kopia/kopia:202 alongside kopia/kopia:201), so batches should be per image and next by filter.

If you need any more info or have any questions, feel free to ask!

[danroc]

@sergi0g, I opened #148, let me know if this is what you had in mind.