I suspect there is no way to do this in git, unless there has been some recent addition. Although the question asked isn't exactly the same, the answers to What is the opposite of `git diff HEAD^`?, Referencing the child of a commit in Git, and How do I find the next commit in Git? (child/children of ref) seem to suggest that there is no way to do this in git.

(Many of the answers erroneously suggest that this is impossible as a matter of principle — but it's not impossible, as git log --oneline --graph --all shows; git just won't let you do it.)