System.err.println("PR head: " + prHead);
        System.err.println("Base: " + baseSha);

        // One SHA per line to stdout so callers can pipe safely.
        System.out.print(stdout("git", "rev-list", baseSha + ".." + prHead));
    }

    private static boolean refExists(String ref) throws IOException, InterruptedException {

        final List<String> specialCommands = Arrays.asList("echo \"test with quotes\"", "echo 'test with single quotes'",
                "echo test with spaces", "echo test&with&ampersand", "echo test|with|pipe");

        generator.setCommandList(specialCommands);
        assertTrue("Special character commands should be settable", true);

        // Test with very long commands