List<String> parentCommits = parentCommitsOf(commit)
        if (parentCommits.size() != 2) {
            println("$commit is not a merge commit we're looking for. Parents: $parentCommits")
            return
        }

        // The correct state we are looking for is:
        // 1. It's a merge commit.
        // 2. One of its parent commits is from master only.