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, 261 deletions

diff --git a/tree_diff.go b/tree_diff.go
deleted file mode 100644
index d5f0377..0000000
--- a/tree_diff.go
+++ /dev/null
@@ -1,261 +0,0 @@
-package git
-
-import (
-	"bytes"
-	"fmt"
-	"io"
-	"sort"
-	"strings"
-
-	"gopkg.in/src-d/go-git.v4/plumbing"
-)
-
-type Action int
-
-func (a Action) String() string {
-	switch a {
-	case Insert:
-		return "Insert"
-	case Delete:
-		return "Delete"
-	case Modify:
-		return "Modify"
-	default:
-		panic(fmt.Sprintf("unsupported action: %d", a))
-	}
-}
-
-const (
-	Insert Action = iota
-	Delete
-	Modify
-)
-
-type Change struct {
-	Action
-	From ChangeEntry
-	To   ChangeEntry
-}
-
-type ChangeEntry struct {
-	Name      string
-	Tree      *Tree
-	TreeEntry TreeEntry
-}
-
-func (c *Change) Files() (from *File, to *File, err error) {
-	if c.Action == Insert || c.Action == Modify {
-		to, err = newFileFromTreeEntry(c.To.Tree, &c.To.TreeEntry)
-		if err != nil {
-			return
-		}
-
-	}
-
-	if c.Action == Delete || c.Action == Modify {
-		from, err = newFileFromTreeEntry(c.From.Tree, &c.From.TreeEntry)
-		if err != nil {
-			return
-		}
-	}
-
-	return
-}
-
-func newFileFromTreeEntry(t *Tree, e *TreeEntry) (*File, error) {
-	blob, err := t.r.Blob(e.Hash)
-	if err != nil {
-		return nil, err
-	}
-
-	return NewFile(e.Name, e.Mode, blob), nil
-}
-
-func (c *Change) String() string {
-	return fmt.Sprintf("<Action: %s, Path: %s>", c.Action, c.name())
-}
-
-func (c *Change) name() string {
-	if c.From.Name != "" {
-		return c.From.Name
-	}
-
-	return c.To.Name
-}
-
-type Changes []*Change
-
-func newEmpty() Changes {
-	return make([]*Change, 0, 0)
-}
-
-func DiffTree(a, b *Tree) ([]*Change, error) {
-	if a == b {
-		return newEmpty(), nil
-	}
-
-	if a == nil || b == nil {
-		return newWithEmpty(a, b)
-	}
-
-	return newDiffTree(a, b)
-}
-
-func (c Changes) Len() int {
-	return len(c)
-}
-
-func (c Changes) Swap(i, j int) {
-	c[i], c[j] = c[j], c[i]
-}
-
-func (c Changes) Less(i, j int) bool {
-	return strings.Compare(c[i].name(), c[j].name()) < 0
-}
-
-func (c Changes) String() string {
-	var buffer bytes.Buffer
-	buffer.WriteString("[")
-	comma := ""
-	for _, v := range c {
-		buffer.WriteString(comma)
-		buffer.WriteString(v.String())
-		comma = ", "
-	}
-	buffer.WriteString("]")
-
-	return buffer.String()
-}
-
-func newWithEmpty(a, b *Tree) (Changes, error) {
-	changes := newEmpty()
-
-	var action Action
-	var tree *Tree
-	if a == nil {
-		action = Insert
-		tree = b
-	} else {
-		action = Delete
-		tree = a
-	}
-
-	w := NewTreeWalker(tree.r, tree, true)
-	defer w.Close()
-
-	for {
-		path, entry, err := w.Next()
-		if err == io.EOF {
-			break
-		} else if err != nil {
-			return nil, fmt.Errorf("cannot get next file: %s", err)
-		}
-
-		if entry.Mode.IsDir() {
-			continue
-		}
-
-		c := &Change{Action: action}
-
-		if action == Insert {
-			c.To.Name = path
-			c.To.TreeEntry = entry
-			c.To.Tree = tree
-		} else {
-			c.From.Name = path
-			c.From.TreeEntry = entry
-			c.From.Tree = tree
-		}
-
-		changes = append(changes, c)
-	}
-
-	return changes, nil
-}
-
-// FIXME: this is very inefficient, but correct.
-// The proper way to do this is to implement a diff-tree algorithm,
-// while taking advantage of the tree hashes to avoid traversing
-// subtrees when the hash is equal in both inputs.
-func newDiffTree(a, b *Tree) ([]*Change, error) {
-	var result []*Change
-
-	aChanges, err := newWithEmpty(a, nil)
-	if err != nil {
-		return nil, fmt.Errorf("cannot create nil-diff of source tree: %s", err)
-	}
-	sort.Sort(aChanges)
-
-	bChanges, err := newWithEmpty(nil, b)
-	if err != nil {
-		return nil, fmt.Errorf("cannot create nil-diff of destination tree: %s", err)
-	}
-	sort.Sort(bChanges)
-
-	for len(aChanges) > 0 && len(bChanges) > 0 {
-		switch comp := strings.Compare(aChanges[0].name(), bChanges[0].name()); {
-		case comp == 0: // append as "Modify" or ignore if not changed
-			modified, err := hasChange(a, b, aChanges[0].name())
-			if err != nil {
-				return nil, err
-			}
-
-			if modified {
-				c := mergeInsertAndDeleteIntoModify(aChanges[0], bChanges[0])
-				result = append(result, c)
-			}
-
-			aChanges = aChanges[1:]
-			bChanges = bChanges[1:]
-		case comp < 0: // delete first a change
-			result = append(result, aChanges[0])
-			aChanges = aChanges[1:]
-		case comp > 0: // insert first b change
-			result = append(result, bChanges[0])
-			bChanges = bChanges[1:]
-		}
-	}
-
-	// append all remaining changes in aChanges, if any, as deletes
-	// append all remaining changes in bChanges, if any, as inserts
-	result = append(result, aChanges...)
-	result = append(result, bChanges...)
-
-	return result, nil
-}
-
-func mergeInsertAndDeleteIntoModify(a, b *Change) *Change {
-	c := &Change{Action: Modify}
-	c.From.Name = a.From.Name
-	c.From.Tree = a.From.Tree
-	c.From.TreeEntry = a.From.TreeEntry
-	c.To.Name = b.To.Name
-	c.To.Tree = b.To.Tree
-	c.To.TreeEntry = b.To.TreeEntry
-
-	return c
-}
-
-func hasChange(a, b *Tree, path string) (bool, error) {
-	ha, err := hash(a, path)
-	if err != nil {
-		return false, err
-	}
-
-	hb, err := hash(b, path)
-	if err != nil {
-		return false, err
-	}
-
-	return ha != hb, nil
-}
-
-func hash(tree *Tree, path string) (plumbing.Hash, error) {
-	file, err := tree.File(path)
-	if err != nil {
-		var empty plumbing.Hash
-		return empty, fmt.Errorf("cannot find file %s in tree: %s", path, err)
-	}
-
-	return file.Hash, nil
-}