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, 79 deletions

diff --git a/difftree/internal/merkletrie/frame.go b/difftree/internal/merkletrie/frame.go
deleted file mode 100644
index a40c6ad..0000000
--- a/difftree/internal/merkletrie/frame.go
+++ /dev/null
@@ -1,79 +0,0 @@
-package merkletrie
-
-import (
-	"bytes"
-	"fmt"
-)
-
-const sep = "/"
-
-// A frame represents siblings in a trie, along with the path to get to
-// them.  For example the frame for the node with key `b` in this trie:
-//
-//                    a
-//                   / \
-//                  /   \
-//                 /     \
-//                b       c
-//               /|\     / \
-//              y z x   d   e
-//                |
-//                g
-//
-// would be:
-//
-//     f := frame{
-//         base: "a/b",           // path to the siblings
-//         stack: []Node{z, y, x} // in reverse alphabetical order
-//     }
-type frame struct {
-	base  string  // absolute key of their parents
-	stack []Noder // siblings, sorted in reverse alphabetical order by key
-}
-
-// newFrame returns a frame for the children of a node n.
-func newFrame(parentAbsoluteKey string, n Noder) *frame {
-	return &frame{
-		base:  parentAbsoluteKey + sep + n.Key(),
-		stack: n.Children(),
-	}
-}
-
-func (f *frame) String() string {
-	var buf bytes.Buffer
-	_, _ = buf.WriteString(fmt.Sprintf("base=%q, stack=[", f.base))
-
-	sep := ""
-	for _, e := range f.stack {
-		_, _ = buf.WriteString(sep)
-		sep = ", "
-		_, _ = buf.WriteString(fmt.Sprintf("%q", e.Key()))
-	}
-
-	_ = buf.WriteByte(']')
-
-	return buf.String()
-}
-
-func (f *frame) top() (Noder, bool) {
-	if len(f.stack) == 0 {
-		return nil, false
-	}
-
-	top := len(f.stack) - 1
-
-	return f.stack[top], true
-}
-
-func (f *frame) pop() (Noder, bool) {
-	if len(f.stack) == 0 {
-		return nil, false
-	}
-
-	top := len(f.stack) - 1
-	ret := f.stack[top]
-	f.stack[top] = nil
-	f.stack = f.stack[:top]
-
-	return ret, true
-}