For an action running on push, how should I find the list of commits included in push?

If I pushed three commits, and the action is on push, how do I find the full list of commits in push?

I can identify latest one by sha, but base_ref documentation says:

This property is only available when the event that triggers a workflow run is a pull_request.

So I assume I can’t use that for push?

The entire event payload for the even that triggered the workflow is part of the github context.  See https://help.github.com/en/articles/contexts-and-expression-syntax-for-github-actions#github-context for more details.