I'd go for something more like `CanReach` (or `CanReachAny`) as the extension method. Commits (or objects) are reachable, but you're returning a list of references, so you need to talk about being able to reach or containing.

For the function, the "OfTheseCommits" is redundant, as it's in the signature that you're passing commits. Maybe something like `ReferencesThatCanReachAny`, though it's not all that good.