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, 449 insertions, 0 deletions

diff --git a/plumbing/object/tree.go b/plumbing/object/tree.go
new file mode 100644
index 0000000..7a8c1a3
--- /dev/null
+++ b/plumbing/object/tree.go
@@ -0,0 +1,449 @@
+package object
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path"
+	"strconv"
+	"strings"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/storer"
+	"gopkg.in/src-d/go-git.v4/utils/ioutil"
+)
+
+const (
+	maxTreeDepth      = 1024
+	startingStackSize = 8
+	submoduleMode     = 0160000
+	directoryMode     = 0040000
+)
+
+// New errors defined by this package.
+var (
+	ErrMaxTreeDepth = errors.New("maximum tree depth exceeded")
+	ErrFileNotFound = errors.New("file not found")
+)
+
+// Tree is basically like a directory - it references a bunch of other trees
+// and/or blobs (i.e. files and sub-directories)
+type Tree struct {
+	Entries []TreeEntry
+	Hash    plumbing.Hash
+
+	s storer.EncodedObjectStorer
+	m map[string]*TreeEntry
+}
+
+// GetTree gets a tree from an object storer and decodes it.
+func GetTree(s storer.EncodedObjectStorer, h plumbing.Hash) (*Tree, error) {
+	o, err := s.EncodedObject(plumbing.TreeObject, h)
+	if err != nil {
+		return nil, err
+	}
+
+	return DecodeTree(s, o)
+}
+
+// DecodeTree decodes an encoded object into a *Tree and associates it to the
+// given object storer.
+func DecodeTree(s storer.EncodedObjectStorer, o plumbing.EncodedObject) (*Tree, error) {
+	t := &Tree{s: s}
+	if err := t.Decode(o); err != nil {
+		return nil, err
+	}
+
+	return t, nil
+}
+
+// TreeEntry represents a file
+type TreeEntry struct {
+	Name string
+	Mode os.FileMode
+	Hash plumbing.Hash
+}
+
+// File returns the hash of the file identified by the `path` argument.
+// The path is interpreted as relative to the tree receiver.
+func (t *Tree) File(path string) (*File, error) {
+	e, err := t.findEntry(path)
+	if err != nil {
+		return nil, ErrFileNotFound
+	}
+
+	blob, err := GetBlob(t.s, e.Hash)
+	if err != nil {
+		return nil, err
+	}
+
+	return NewFile(path, e.Mode, blob), nil
+}
+
+// TreeEntryFile returns the *File for a given *TreeEntry.
+func (t *Tree) TreeEntryFile(e *TreeEntry) (*File, error) {
+	blob, err := GetBlob(t.s, e.Hash)
+	if err != nil {
+		return nil, err
+	}
+
+	return NewFile(e.Name, e.Mode, blob), nil
+}
+
+func (t *Tree) findEntry(path string) (*TreeEntry, error) {
+	pathParts := strings.Split(path, "/")
+
+	var tree *Tree
+	var err error
+	for tree = t; len(pathParts) > 1; pathParts = pathParts[1:] {
+		if tree, err = tree.dir(pathParts[0]); err != nil {
+			return nil, err
+		}
+	}
+
+	return tree.entry(pathParts[0])
+}
+
+var errDirNotFound = errors.New("directory not found")
+
+func (t *Tree) dir(baseName string) (*Tree, error) {
+	entry, err := t.entry(baseName)
+	if err != nil {
+		return nil, errDirNotFound
+	}
+
+	obj, err := t.s.EncodedObject(plumbing.TreeObject, entry.Hash)
+	if err != nil {
+		return nil, err
+	}
+
+	tree := &Tree{s: t.s}
+	tree.Decode(obj)
+
+	return tree, nil
+}
+
+var errEntryNotFound = errors.New("entry not found")
+
+func (t *Tree) entry(baseName string) (*TreeEntry, error) {
+	if t.m == nil {
+		t.buildMap()
+	}
+	entry, ok := t.m[baseName]
+	if !ok {
+		return nil, errEntryNotFound
+	}
+
+	return entry, nil
+}
+
+// Files returns a FileIter allowing to iterate over the Tree
+func (t *Tree) Files() *FileIter {
+	return NewFileIter(t.s, t)
+}
+
+// ID returns the object ID of the tree. The returned value will always match
+// the current value of Tree.Hash.
+//
+// ID is present to fulfill the Object interface.
+func (t *Tree) ID() plumbing.Hash {
+	return t.Hash
+}
+
+// Type returns the type of object. It always returns plumbing.TreeObject.
+func (t *Tree) Type() plumbing.ObjectType {
+	return plumbing.TreeObject
+}
+
+// Decode transform an plumbing.EncodedObject into a Tree struct
+func (t *Tree) Decode(o plumbing.EncodedObject) (err error) {
+	if o.Type() != plumbing.TreeObject {
+		return ErrUnsupportedObject
+	}
+
+	t.Hash = o.Hash()
+	if o.Size() == 0 {
+		return nil
+	}
+
+	t.Entries = nil
+	t.m = nil
+
+	reader, err := o.Reader()
+	if err != nil {
+		return err
+	}
+	defer ioutil.CheckClose(reader, &err)
+
+	r := bufio.NewReader(reader)
+	for {
+		mode, err := r.ReadString(' ')
+		if err != nil {
+			if err == io.EOF {
+				break
+			}
+
+			return err
+		}
+
+		fm, err := t.decodeFileMode(mode[:len(mode)-1])
+		if err != nil && err != io.EOF {
+			return err
+		}
+
+		name, err := r.ReadString(0)
+		if err != nil && err != io.EOF {
+			return err
+		}
+
+		var hash plumbing.Hash
+		if _, err = io.ReadFull(r, hash[:]); err != nil {
+			return err
+		}
+
+		baseName := name[:len(name)-1]
+		t.Entries = append(t.Entries, TreeEntry{
+			Hash: hash,
+			Mode: fm,
+			Name: baseName,
+		})
+	}
+
+	return nil
+}
+
+func (t *Tree) decodeFileMode(mode string) (os.FileMode, error) {
+	fm, err := strconv.ParseInt(mode, 8, 32)
+	if err != nil && err != io.EOF {
+		return 0, err
+	}
+
+	m := os.FileMode(fm)
+	switch fm {
+	case 0040000: //tree
+		m = m | os.ModeDir
+	case 0120000: //symlink
+		m = m | os.ModeSymlink
+	}
+
+	return m, nil
+}
+
+// Encode transforms a Tree into a plumbing.EncodedObject.
+func (t *Tree) Encode(o plumbing.EncodedObject) error {
+	o.SetType(plumbing.TreeObject)
+	w, err := o.Writer()
+	if err != nil {
+		return err
+	}
+
+	var size int
+	defer ioutil.CheckClose(w, &err)
+	for _, entry := range t.Entries {
+		n, err := fmt.Fprintf(w, "%o %s", entry.Mode, entry.Name)
+		if err != nil {
+			return err
+		}
+
+		size += n
+		n, err = w.Write([]byte{0x00})
+		if err != nil {
+			return err
+		}
+
+		size += n
+		n, err = w.Write([]byte(entry.Hash[:]))
+		if err != nil {
+			return err
+		}
+		size += n
+	}
+
+	o.SetSize(int64(size))
+	return err
+}
+
+func (t *Tree) buildMap() {
+	t.m = make(map[string]*TreeEntry)
+	for i := 0; i < len(t.Entries); i++ {
+		t.m[t.Entries[i].Name] = &t.Entries[i]
+	}
+}
+
+// treeEntryIter facilitates iterating through the TreeEntry objects in a Tree.
+type treeEntryIter struct {
+	t   *Tree
+	pos int
+}
+
+func (iter *treeEntryIter) Next() (TreeEntry, error) {
+	if iter.pos >= len(iter.t.Entries) {
+		return TreeEntry{}, io.EOF
+	}
+	iter.pos++
+	return iter.t.Entries[iter.pos-1], nil
+}
+
+// TreeWalker provides a means of walking through all of the entries in a Tree.
+type TreeWalker struct {
+	stack     []treeEntryIter
+	base      string
+	recursive bool
+
+	s storer.EncodedObjectStorer
+	t *Tree
+}
+
+// NewTreeWalker returns a new TreeWalker for the given tree.
+//
+// It is the caller's responsibility to call Close() when finished with the
+// tree walker.
+func NewTreeWalker(t *Tree, recursive bool) *TreeWalker {
+	stack := make([]treeEntryIter, 0, startingStackSize)
+	stack = append(stack, treeEntryIter{t, 0})
+
+	return &TreeWalker{
+		stack:     stack,
+		recursive: recursive,
+
+		s: t.s,
+		t: t,
+	}
+}
+
+// Next returns the next object from the tree. Objects are returned in order
+// and subtrees are included. After the last object has been returned further
+// calls to Next() will return io.EOF.
+//
+// In the current implementation any objects which cannot be found in the
+// underlying repository will be skipped automatically. It is possible that this
+// may change in future versions.
+func (w *TreeWalker) Next() (name string, entry TreeEntry, err error) {
+	var obj Object
+	for {
+		current := len(w.stack) - 1
+		if current < 0 {
+			// Nothing left on the stack so we're finished
+			err = io.EOF
+			return
+		}
+
+		if current > maxTreeDepth {
+			// We're probably following bad data or some self-referencing tree
+			err = ErrMaxTreeDepth
+			return
+		}
+
+		entry, err = w.stack[current].Next()
+		if err == io.EOF {
+			// Finished with the current tree, move back up to the parent
+			w.stack = w.stack[:current]
+			w.base, _ = path.Split(w.base)
+			w.base = path.Clean(w.base) // Remove trailing slash
+			continue
+		}
+
+		if err != nil {
+			return
+		}
+
+		if entry.Mode == submoduleMode {
+			err = nil
+			continue
+		}
+
+		if entry.Mode.IsDir() {
+			obj, err = GetTree(w.s, entry.Hash)
+		}
+
+		name = path.Join(w.base, entry.Name)
+
+		if err != nil {
+			err = io.EOF
+			return
+		}
+
+		break
+	}
+
+	if !w.recursive {
+		return
+	}
+
+	if t, ok := obj.(*Tree); ok {
+		w.stack = append(w.stack, treeEntryIter{t, 0})
+		w.base = path.Join(w.base, entry.Name)
+	}
+
+	return
+}
+
+// Tree returns the tree that the tree walker most recently operated on.
+func (w *TreeWalker) Tree() *Tree {
+	current := len(w.stack) - 1
+	if w.stack[current].pos == 0 {
+		current--
+	}
+
+	if current < 0 {
+		return nil
+	}
+
+	return w.stack[current].t
+}
+
+// Close releases any resources used by the TreeWalker.
+func (w *TreeWalker) Close() {
+	w.stack = nil
+}
+
+// TreeIter provides an iterator for a set of trees.
+type TreeIter struct {
+	storer.EncodedObjectIter
+	s storer.EncodedObjectStorer
+}
+
+// NewTreeIter returns a TreeIter for the given repository and underlying
+// object iterator.
+//
+// The returned TreeIter will automatically skip over non-tree objects.
+func NewTreeIter(s storer.EncodedObjectStorer, iter storer.EncodedObjectIter) *TreeIter {
+	return &TreeIter{iter, s}
+}
+
+// Next moves the iterator to the next tree and returns a pointer to it. If it
+// has reached the end of the set it will return io.EOF.
+func (iter *TreeIter) Next() (*Tree, error) {
+	for {
+		obj, err := iter.EncodedObjectIter.Next()
+		if err != nil {
+			return nil, err
+		}
+
+		if obj.Type() != plumbing.TreeObject {
+			continue
+		}
+
+		return DecodeTree(iter.s, obj)
+	}
+}
+
+// ForEach call the cb function for each tree contained on this iter until
+// an error happens or the end of the iter is reached. If ErrStop is sent
+// the iteration is stop but no error is returned. The iterator is closed.
+func (iter *TreeIter) ForEach(cb func(*Tree) error) error {
+	return iter.EncodedObjectIter.ForEach(func(obj plumbing.EncodedObject) error {
+		if obj.Type() != plumbing.TreeObject {
+			return nil
+		}
+
+		t, err := DecodeTree(iter.s, obj)
+		if err != nil {
+			return err
+		}
+
+		return cb(t)
+	})
+}