User Story

As a user of the rebase bot, I want to be able to run a lifecycle hook script that automatically identifies the latest branch or release that meets my criteria. This way, I can perform rebases from the most up-to-date branch without needing to manually update it after each release.

Steps

• define an optional "get-base-sha" hook in the rebasebot (at the beginning), with no hook specified we retain the current behaviour
• have the hook return a git SHA,git branch, or git tag(GH release)
• have the rebasebot use that as the rebase base from the source repo
• define a builtin hook script that "get-latest-stable-github-release-base-sha", that can optionally be used as a "get-base-sha" hook
• Enable this feature on applicable rebases in CI.

Stakeholders

• cluster infra
• Other rebase bot users (no requests for this yet)

Definition of Done

• Rebasebot is able to execute user provided script that returns source branch/tag and use it as source repository

• Docs

• README is updated to document the feature

• Testing

• Test for the functionality.