Fix commit.File() gorutine leak

Commit.File() was leaking a goroutine because it was looping over
an iterator without closing its channel.

Now commit.File() calls the new Tree.File() method that searches
the file in the repository by trasversing the dir tree instead
of using the tree.Files() iterator.

This not only prevent the goroutine leak, but also speeds up
file searching.

1 files changed, 80 insertions, 0 deletions

diff --git a/tree.go b/tree.go
index 7b988a1..232bfc2 100644
--- a/tree.go
+++ b/tree.go
@@ -2,10 +2,12 @@ package git
 
 import (
 	"bufio"
+	"errors"
 	"io"
 	"os"
 	"path/filepath"
 	"strconv"
+	"strings"
 
 	"gopkg.in/src-d/go-git.v2/core"
 )
@@ -26,6 +28,84 @@ type TreeEntry struct {
 	Hash core.Hash
 }
 
+// New errors defined by this package.
+var ErrFileNotFound = errors.New("file not found")
+
+func (t *Tree) File(path string) (*File, error) {
+	hash, err := t.hashOf(path)
+	if err != nil {
+		return nil, ErrFileNotFound
+	}
+
+	obj, ok := t.r.Storage.Get(*hash)
+	if !ok {
+		return nil, ErrFileNotFound // a git submodule
+	}
+
+	if obj.Type() != core.BlobObject {
+		return nil, ErrFileNotFound // a directory
+	}
+
+	blob := &Blob{}
+	blob.Decode(obj)
+
+	return &File{Name: path, Reader: blob.Reader(), Hash: *hash}, nil
+}
+
+func (t *Tree) hashOf(path string) (*core.Hash, 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
+		}
+	}
+
+	entry, err := tree.entry(pathParts[0])
+	if err != nil {
+		return nil, err
+	}
+
+	return &entry.Hash, nil
+}
+
+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, ok := t.r.Storage.Get(entry.Hash)
+	if !ok { // git submodule
+		return nil, errDirNotFound
+	}
+
+	if obj.Type() != core.TreeObject {
+		return nil, errDirNotFound // a file
+	}
+
+	tree := &Tree{r: t.r}
+	tree.Decode(obj)
+
+	return tree, nil
+}
+
+var errEntryNotFound = errors.New("entry not found")
+
+func (t *Tree) entry(baseName string) (*TreeEntry, error) {
+	for _, entry := range t.Entries {
+		if entry.Name == baseName {
+			return &entry, nil
+		}
+	}
+
+	return nil, errEntryNotFound
+}
+
 func (t *Tree) Files() chan *File {
 	ch := make(chan *File, 1)