plumbing/object: move difftree to object package

- To avoid ciclic dependency errors, we move all the difftree files to object package.
- Added Diff method to Tree object.

1 files changed, 4 insertions, 0 deletions

diff --git a/plumbing/object/tree.go b/plumbing/object/tree.go
index 436ac32..d39c315 100644
--- a/plumbing/object/tree.go
+++ b/plumbing/object/tree.go
@@ -299,6 +299,10 @@ func (t *Tree) buildMap() {
 	}
 }
 
+func (from *Tree) Diff(to *Tree) (Changes, error) {
+	return DiffTree(from, to)
+}
+
 // treeEntryIter facilitates iterating through the TreeEntry objects in a Tree.
 type treeEntryIter struct {
 	t   *Tree