move plumbing from top level package to plumbing (#183)

* plumbing: rename Object -> EncodedObject.

* plumbing/storer: rename ObjectStorer -> EncodedObjectStorer.

* move difftree to plumbing/difftree.

* move diff -> utils/diff

* make Object/Tag/Blob/Tree/Commit/File depend on storer.

* Object and its implementations now depend only on
  storer.EncodedObjectStorer, not git.Repository.
* Tests are decoupled accordingly.

* move Object/Commit/File/Tag/Tree to plumbing/object.

* move Object/Commit/File/Tag/Tree to plumbing/object.
* move checkClose to utils/ioutil.

* move RevListObjects to plumbing/revlist.Objects.

* move DiffTree to plumbing/difftree package.

* rename files with plural nouns to singular

* plumbing/object: add GetBlob/GetCommit/GetTag/GetTree.

1 files changed, 3 insertions, 3 deletions

diff --git a/plumbing/format/packfile/diff_delta.go b/plumbing/format/packfile/diff_delta.go
index fb05a79..bc4fafa 100644
--- a/plumbing/format/packfile/diff_delta.go
+++ b/plumbing/format/packfile/diff_delta.go
@@ -17,17 +17,17 @@ const (
 
 // GetOFSDelta returns an offset delta that knows the way of how to transform
 // base object to target object
-func GetOFSDelta(base, target plumbing.Object) (plumbing.Object, error) {
+func GetOFSDelta(base, target plumbing.EncodedObject) (plumbing.EncodedObject, error) {
 	return getDelta(base, target, plumbing.OFSDeltaObject)
 }
 
 // GetRefDelta returns a reference delta that knows the way of how to transform
 // base object to target object
-func GetRefDelta(base, target plumbing.Object) (plumbing.Object, error) {
+func GetRefDelta(base, target plumbing.EncodedObject) (plumbing.EncodedObject, error) {
 	return getDelta(base, target, plumbing.REFDeltaObject)
 }
 
-func getDelta(base, target plumbing.Object, t plumbing.ObjectType) (plumbing.Object, error) {
+func getDelta(base, target plumbing.EncodedObject, t plumbing.ObjectType) (plumbing.EncodedObject, error) {
 	if t != plumbing.OFSDeltaObject && t != plumbing.REFDeltaObject {
 		return nil, fmt.Errorf("Type not supported: %v", t)
 	}