使用JGit获取指定分支的文件内容

/**
     * 获取指定分支、指定文件的内容
     * @param gitRoot git仓库目录
     * @param branchName 分支名称
     * @param fileName 文件名称
     * @return
     * @throws Exception
     */
    public static String getContentWithFile(String gitRoot, final String branchName, String fileName)
                                                                                                     throws Exception {
        final Git git = Git.open(new File(gitRoot));
        Repository repository = git.getRepository();

        repository = git.getRepository();
        RevWalk walk = new RevWalk(repository);
        Ref ref = repository.getRef(branchName);
        if (ref == null) {
            //获取远程分支
            ref = repository.getRef(REF_REMOTES + branchName);
        }
        //异步pull
        ExecutorService executor = Executors.newCachedThreadPool();
        FutureTask<Boolean> task = new FutureTask<Boolean>(new Callable<Boolean>() {
            @Override
            public Boolean call() throws Exception {
                /*//创建分支
                CreateBranchCommand createBranchCmd = git.branchCreate();
                createBranchCmd.setStartPoint(REF_REMOTES + branchName).setName(branchName).call();*/
                return git.pull().call().isSuccessful();
            }
        });
        executor.execute(task);

        ObjectId objId = ref.getObjectId();
        RevCommit revCommit = walk.parseCommit(objId);
        RevTree revTree = revCommit.getTree();

        TreeWalk treeWalk = TreeWalk.forPath(repository, fileName, revTree);
        //文件名错误
        if (treeWalk == null)
            return null;

        ObjectId blobId = treeWalk.getObjectId(0);
        ObjectLoader loader = repository.open(blobId);
        byte[] bytes = loader.getBytes();
        if (bytes != null)
            return new String(bytes);
        return null;
    }