JGit: Is there a thread safe way to add and update files

Question

The easy way to add or update files in JGit is like this:

  git.add().addFilepattern(file).call()

But that assumes that the file exists in the Git working directory. If I have a multi-threaded setup (using Scala and Akka), is there a way to work only on a bare repository, writing the data directly to JGit, avoiding having to first write the file in the working directory?

For getting the file, that seems to work with:

  git.getRepository().open(objId).getBytes()

Is there something similar for adding or updating files?

Answer 1

"Add" is a high-level abstraction that places a file in the index. In a bare repository, you lack an index, so this is not a 1:1 correspondence between the functionality. Instead, you can create a file in a new commit. To do this, you would use an ObjectInserter to add objects to the repository (one per thread, please). Then you would:

1. Add the contents of the file to the repository, as a blob, by inserting its bytes (or providing an InputStream).

2. Create a tree that includes the new file, by using a TreeFormatter.

3. Create a commit that points to the tree, by using a CommitBuilder.

For example, to create a new commit (with no parents) that contains only your file:

ObjectInserter repoInserter = repository.newObjectInserter();
ObjectId blobId;

try
{
    // Add a blob to the repository
    ObjectId blobId = repoInserter.insert(OBJ_BLOB, "Hello World!\n".getBytes());

    // Create a tree that contains the blob as file "hello.txt"
    TreeFormatter treeFormatter = new TreeFormatter();
    treeFormatter.append("hello.txt", FileMode.TYPE_FILE, blobId);
    ObjectId treeId = treeFormatter.insertTo(repoInserter);

    // Create a commit that contains this tree
    CommitBuilder commit = new CommitBuilder();
    PersonIdent ident = new PersonIdent("Me", "[email protected]");
    commit.setCommitter(ident);
    commit.setAuthor(ident);
    commit.setMessage("This is a new commit!");
    commit.setTreeId(treeId);

    ObjectId commitId = repositoryInserter.insert(commit);

    repoInserter.flush();
}
finally
{
    repoInserter.release();
}

Now you can git checkout the commit id returned as commitId.