如何“猫”在JGit文件？

Question

一个而回我一直在寻找在Java中嵌入分布式版本控制系统， 我想我已经发现它在 JGit ，这是混帐的纯Java实现。 然而，没有在示例代码或教程的方式很多。

如何用JGit来检索某个文件的HEAD版本（就像svn cat或hg cat做对子级）？

我想这涉及到一些REV-树遍历和正在寻找一个代码示例。

Answer 1

不幸的是蒂洛的回答不与最新的JGit API工作。这里是我找到了解决办法：

File repoDir = new File("test-git");
// open the repository
Repository repository = new Repository(repoDir);
// find the HEAD
ObjectId lastCommitId = repository.resolve(Constants.HEAD);
// now we have to get the commit
RevWalk revWalk = new RevWalk(repository);
RevCommit commit = revWalk.parseCommit(lastCommitId);
// and using commit's tree find the path
RevTree tree = commit.getTree();
TreeWalk treeWalk = new TreeWalk(repository);
treeWalk.addTree(tree);
treeWalk.setRecursive(true);
treeWalk.setFilter(PathFilter.create(path));
if (!treeWalk.next()) {
  return null;
}
ObjectId objectId = treeWalk.getObjectId(0);
ObjectLoader loader = repository.open(objectId);

// and then one can use either
InputStream in = loader.openStream()
// or
loader.copyTo(out)

我希望它是简单。

Answer 2

下面是@ morisil的回答的一个简化版本，使用的一些概念从@directed笑的并用JGit 2.2.0测试：

private String fetchBlob(String revSpec, String path) throws MissingObjectException, IncorrectObjectTypeException,
        IOException {

    // Resolve the revision specification
    final ObjectId id = this.repo.resolve(revSpec);

    // Makes it simpler to release the allocated resources in one go
    ObjectReader reader = this.repo.newObjectReader();

    try {
        // Get the commit object for that revision
        RevWalk walk = new RevWalk(reader);
        RevCommit commit = walk.parseCommit(id);

        // Get the revision's file tree
        RevTree tree = commit.getTree();
        // .. and narrow it down to the single file's path
        TreeWalk treewalk = TreeWalk.forPath(reader, path, tree);

        if (treewalk != null) {
            // use the blob id to read the file's data
            byte[] data = reader.open(treewalk.getObjectId(0)).getBytes();
            return new String(data, "utf-8");
        } else {
            return "";
        }
    } finally {
        reader.release();
    }
}

repo是如在其他的答案创建的Repository对象。

Answer 3

我跟着@蒂洛的和@ morisil的回答让这一点，与JGit 1.2.0兼容：

File repoDir = new File("test-git/.git");
// open the repository
Repository repo = new Repository(repoDir);
// find the HEAD
Commit head = repo.mapCommit(Constants.HEAD);
// retrieve the tree in HEAD
Tree tree = head.getTree();

// 1.2.0 api version here
// find a file (as a TreeEntry, which contains the blob object id)
TreeWalk treewalk = TreeWalk.forPath(repo, "b/test.txt", tree);
// use the blob id to read the file's data
byte[] data = repo.open(treewalk.getObjectId(0)).getBytes();

我没有测试的Java版本，但它应该工作。它从转换

(.getBytes (.open repo (.getObjectId (TreeWalk/forPath repo "b/test.txt" tree) 0)))

Clojure中（以下相同的设置作为顶部部分），它确实工作。

Answer 4

想通了通过自己。 API是相当底层的，但它不是太糟糕了：

File repoDir = new File("test-git/.git");
// open the repository
Repository repo = new Repository(repoDir);
// find the HEAD
Commit head = repo.mapCommit(Constants.HEAD);
// retrieve the tree in HEAD
Tree tree = head.getTree();
// find a file (as a TreeEntry, which contains the blob object id)
TreeEntry entry = tree.findBlobMember("b/test.txt");
// use the blob id to read the file's data
byte[] data = repo.openBlob(entry.getId()).getBytes();

Answer 5

我已经开始写了一个名为库 gitective 包含许多助手与斑点工作，提交，使用JGit和是树木MIT-授权和可用在GitHub。

获取在HEAD文件的内容提交

Repository repo = new FileRepository("/repos/project/.git");
String content = BlobUtils.getHeadContent(repo, "src/Buffer.java");

获取的一个分支的文件的内容

Repository repo = new FileRepository("/repos/project/.git");
String content = BlobUtils.getContent(repo, "master", "src/Buffer.java");

<强>不同的两个文件

Repository repo = new FileRepository("/repos/project/.git");
ObjectId current = BlobUtils.getId(repo, "master", "Main.java");
ObjectId previous = BlobUtils.getId(repo, "master~1", "Main.java");
Collection<Edit> edit = BlobUtils.diff(repo, previous, current);

的设置在自述详述实用程序的详细例子。

Answer 6

有在 JGit教程（但也既不是真正有用的还是完整的，因为它们很可能切换到过时日食在没有文档尚未提供）。

Answer 7

可以如下读取一个给定的文件路径的内容。请注意，对树遍历可以的无效的，如果没有路径是在给定的树中。因此它需要一些特定的处理。

public String readFile(RevCommit commit, String filepath) throws IOException {
    try (TreeWalk walk = TreeWalk.forPath(repo, filepath, commit.getTree())) {
        if (walk != null) {
            byte[] bytes = repo.open(walk.getObjectId(0)).getBytes();
            return new String(bytes, StandardCharsets.UTF_8);
        } else {
            throw new IllegalArgumentException("No path found.");
        }
    }
}

例如：

ObjectId head = repo.resolve(Constants.HEAD);
RevCommit last = repo.parseCommit(head);
readFile(last, "docs/README.md")

此答案被写入与JGit 4.8.0。