run git commands from java

Git.java

public class Git {

    private static List<Path> allFilesInDirectory(Path directory) throws IOException {
        final List<Path> files = new ArrayList<>();
        Files.walkFileTree(directory, new SimpleFileVisitor<Path>() {
            @Override
            public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
                if (dir.endsWith(".git")) {
                    return FileVisitResult.SKIP_SUBTREE;
                }
                return FileVisitResult.CONTINUE;
            }

            @Override
            public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
                if (attrs.isRegularFile()) {
                    files.add(file);
                }
                return FileVisitResult.CONTINUE;
            }
        });
        return files;
    }

    public static void gitInit(Path directory) throws IOException, InterruptedException {
        runCommand(directory, "git", "init");
    }

    public static void gitStage(Path directory) throws IOException, InterruptedException {
        runCommand(directory, "git", "add", "-A");
    }

    public static void gitCommit(Path directory, String message) throws IOException, InterruptedException {
        runCommand(directory, "git", "commit", "-m", message);
    }

    public static void gitGc(Path directory) throws IOException, InterruptedException {
        runCommand(directory, "git", "gc");
    }

    public static void runCommand(Path directory, String... command) throws IOException, InterruptedException {
        ProcessBuilder pb = new ProcessBuilder()
                .command(command)
                .directory(directory.toFile());
        Process p = pb.start();
        StreamGobbler errorGobbler = new StreamGobbler(p.getErrorStream(), "ERROR");
        StreamGobbler outputGobbler = new StreamGobbler(p.getInputStream(), "OUTPUT");
        outputGobbler.start();
        errorGobbler.start();
        int exit = p.waitFor();
        errorGobbler.join();
        outputGobbler.join();
        if (exit != 0) {
            throw new AssertionError(String.format("runCommand returned %d", exit));
        }
    }

    private static class StreamGobbler extends Thread {

        InputStream is;
        String type;

        private StreamGobbler(InputStream is, String type) {
            this.is = is;
            this.type = type;
        }

        @Override
        public void run() {
            try {
                InputStreamReader isr = new InputStreamReader(is);
                BufferedReader br = new BufferedReader(isr);
                String line = null;
                while ((line = br.readLine()) != null) {
                    System.out.println(type + "> " + line);
                }
            } catch (IOException ioe) {
                ioe.printStackTrace();
            }
        }
    }
}