Looking up *object.Commit from SHA string doesn't seem like something you want to make every Checker implementation do (even if it's mostly boilerplate), so pas

Looking up *object.Commit from SHA string doesn't seem like something you want to make every Checker implementation do (even if it's mostly boilerplate), so passing a higher-level object makes sense here. What you might want to do is also define an interface for what Git calls "commit-ish"[0] objects, and use that in place of *object.Commit. Then you could pass e.g. *object.Tag in place of *object.Commit. Think of the interface as a contract between implementations and users of the data structure. Typically, you use an interface when multiple implementations are capable of fulfilling the same contract. If there's only one implementation, you likely don't need an interface—for instance, you can ignore my suggestion about abstracting commit-ish if you're pretty sure your checker would never be called for a tag. Interfaces are often useful when testing, because a mock implementation can fulfill that same contract. For instance, you might implement a *object.MockCommit which just uses static values instead of actually operating on a Git repository, and then pass that for your commit-ish in unit tests for various Checkers. [0] https://git-scm.com/docs/gitglossary#Documentation/gitglossary.txt-aiddefcommit-ishacommit-ishalsocommittish https://git-scm.com/docs/gitglossary#Documentation/gitglossa...