TreeWalk treeWalk = new TreeWalk(reader);
treeWalk.setRecursive(true);
treeWalk.addTree(headCommit.getTree());
treeWalk.addTree(new DirCacheIterator(cache));
treeWalk.addTree(new FileTreeIterator(repo));
treeWalk.setFilter(AndTreeFilter.create(new SkipWorkTreeFilter(
1), new IndexDiffFilter(1, 2)));
// Return null if no local changes to stash
if (!treeWalk.next())
return null;