System.exit(1)
        }

        List<String> commits = Files.readAllLines(Paths.get(args[0]))
        try {
            commits.each { checkCommit(it) }
        } finally {
            THREAD_POOL.shutdown()
        }
    }

    static void checkCommit(String commit) {
        List<String> parentCommits = parentCommitsOf(commit)
        if (parentCommits.size() != 2) {