[JGIT RFC] How read versions of a specific object

Hi,

I am trying to read all or n-th version of an object. Currently to do this I am using the following piece of code, which has to walk to every commit is present and from there prepare a set of its object id, it is definitely expensive if the commit history is huge, is there a faster/better way to achieve it?

for (int i = 0; i < App.OBJECT_COUNT;
            ++i) {
            System.out.println("INDEX: " + i);
            String isbn =
                String.valueOf(Integer.parseInt(App.INIT_ID) + i);
            System.out.println("ISBN: " + isbn);
            ObjectWalk objectWalk = new ObjectWalk(repo);
            /*
             * Checks whether the Commit has the tree or not. It does not
             * check whether it has changed or not.
             */
            objectWalk.setTreeFilter(PathFilter.create(isbn));
            RevObject revObject = null;
            objectWalk.markStart(objectWalk.parseCommit(repo.resolve(
                Constants.HEAD)));
            Set<ObjectId> revisions =
                new HashSet<ObjectId>();
            do {
                if (revObject != null) {
                    Commit revision = repo.mapCommit(revObject.getId());
                    Tree versionTree = repo.mapTree(revision.getTreeId());
                    if (versionTree.existsBlob(isbn)) {
                        revisions.add(versionTree.findBlobMember(isbn).getId());
                    }
                }
                revObject = objectWalk.next();
            }
            while (revObject != null);
            System.out.println("Revisions: " + revisions);
        }

The details source code of the project is available @ http://github.com/imyousuf/jgit-usage/tree/master

Thank you,