Support drafter releaser with multiple branches for libraries

[dmikusa]

Describe the Enhancement

When using pipeline-builder to support deploying a library, like libcnb or libpak, we want to be able to support multiple version lines. This requires draft releaser to be able to watch PRs sent against a specific branch and filter out just those.

For example, it would watch the main branch for 2.x releases and the release-1.x branch for changes to the 1.x branch.

Draft releaser is located at https://github.com/paketo-buildpacks/pipeline-builder/tree/main/actions/draft-release.

Motivation

We are doing this already but having to manually tag releases for the non-primary branch and it's painful.

[dmikusa]

Hmm, maybe this request is for "better" support.

You can actually make the draft releaser work with multiple branches now. To do it, what you need is a PR that's merged recently on the branch on which you want to update the draft release notes. Either commit that PR, or go back find the action from it and re-run the draft releaser action. That'll go and update the "draft release" to have notes from that draft.

It works, but it is cumbersome because you can't directly run the draft release workflow. It only updates on merge with your branch, or you can re-run an old action. Maybe an option is to just make it workflow-triggerable so you can click and run it, or maybe we look at just dropping it in use of the built-in Github functionality. Although, I do kind of like how the draft release notes accumulate so you can see what is pending release easily.