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, 0 insertions, 20 deletions

diff --git a/difftree/internal/merkletrie/noder.go b/difftree/internal/merkletrie/noder.go
deleted file mode 100644
index 3566657..0000000
--- a/difftree/internal/merkletrie/noder.go
+++ /dev/null
@@ -1,20 +0,0 @@
-package merkletrie
-
-// The Noder interface is implemented by the elements of a Merkle Trie.
-type Noder interface {
-	// Hash returns the hash of the element.
-	Hash() []byte
-	// Key returns the key of the element.
-	Key() string
-	// Children returns the children of the element, sorted
-	// in reverse key alphabetical order.
-	Children() []Noder
-	// NumChildren returns the number of children this element has.
-	//
-	// This method is an optimization: the number of children is easily
-	// calculated as the length of the value returned by the Children
-	// method (above); yet, some implementations will be able to
-	// implement NumChildren in O(1) while Children is usually more
-	// complex.
-	NumChildren() int
-}