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, 67 deletions

diff --git a/commit_walker.go b/commit_walker.go
deleted file mode 100644
index 8685801..0000000
--- a/commit_walker.go
+++ /dev/null
@@ -1,67 +0,0 @@
-package git
-
-import (
-	"io"
-
-	"gopkg.in/src-d/go-git.v4/plumbing"
-)
-
-type commitWalker struct {
-	seen  map[plumbing.Hash]bool
-	stack []*CommitIter
-	start *Commit
-	cb    func(*Commit) error
-}
-
-// WalkCommitHistory walks the commit history
-func WalkCommitHistory(c *Commit, cb func(*Commit) error) error {
-	w := &commitWalker{
-		seen:  make(map[plumbing.Hash]bool),
-		stack: make([]*CommitIter, 0),
-		start: c,
-		cb:    cb,
-	}
-
-	return w.walk()
-}
-
-func (w *commitWalker) walk() error {
-	var commit *Commit
-
-	if w.start != nil {
-		commit = w.start
-		w.start = nil
-	} else {
-		current := len(w.stack) - 1
-		if current < 0 {
-			return nil
-		}
-
-		var err error
-		commit, err = w.stack[current].Next()
-		if err == io.EOF {
-			w.stack = w.stack[:current]
-			return w.walk()
-		}
-
-		if err != nil {
-			return err
-		}
-	}
-
-	// check and update seen
-	if w.seen[commit.Hash] {
-		return w.walk()
-	}
-
-	w.seen[commit.Hash] = true
-	if commit.NumParents() > 0 {
-		w.stack = append(w.stack, commit.Parents())
-	}
-
-	if err := w.cb(commit); err != nil {
-		return err
-	}
-
-	return w.walk()
-}