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.

3 files changed, 215 insertions, 10 deletions

diff --git a/commit.go b/commit.go
index 1dd09ab..ea6419f 100644
--- a/commit.go
+++ b/commit.go
@@ -3,7 +3,6 @@ package git
 import (
 	"bufio"
 	"bytes"
-	"errors"
 	"fmt"
 	"io"
 	"sort"
@@ -11,9 +10,6 @@ import (
 	"gopkg.in/src-d/go-git.v2/core"
 )
 
-// New errors defined by this package.
-var ErrFileNotFound = errors.New("file not found")
-
 type Hash core.Hash
 
 // Commit points to a single tree, marking it as what the project looked like
@@ -59,12 +55,7 @@ func (c *Commit) NumParents() int {
 // nil error if the file exists. If the file does not exists, it returns
 // a nil file and the ErrFileNotFound error.
 func (c *Commit) File(path string) (file *File, err error) {
-	for file := range c.Tree().Files() {
-		if file.Name == path {
-			return file, nil
-		}
-	}
-	return nil, ErrFileNotFound
+	return c.Tree().File(path)
 }
 
 // Decode transform an core.Object into a Blob struct
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)
 
diff --git a/tree_test.go b/tree_test.go
new file mode 100644
index 0000000..049161c
--- /dev/null
+++ b/tree_test.go
@@ -0,0 +1,134 @@
+package git
+
+import (
+	"os"
+
+	"gopkg.in/src-d/go-git.v2/core"
+	"gopkg.in/src-d/go-git.v2/formats/packfile"
+
+	. "gopkg.in/check.v1"
+)
+
+type SuiteTree struct {
+	repos map[string]*Repository
+}
+
+var _ = Suite(&SuiteTree{})
+
+// create the repositories of the fixtures
+func (s *SuiteTree) SetUpSuite(c *C) {
+	fixtureRepos := [...]struct {
+		url      string
+		packfile string
+	}{
+		{"https://github.com/tyba/git-fixture.git", "formats/packfile/fixtures/git-fixture.ofs-delta"},
+		{"https://github.com/cpcs499/Final_Pres_P.git", "formats/packfile/fixtures/Final_Pres_P.ofs-delta"},
+		{"https://github.com/jamesob/desk.git", "formats/packfile/fixtures/jamesob-desk.pack"},
+		{"https://github.com/spinnaker/spinnaker.git", "formats/packfile/fixtures/spinnaker-spinnaker.pack"},
+		{"https://github.com/alcortesm/binary-relations.git", "formats/packfile/fixtures/alcortesm-binary-relations.pack"},
+	}
+	s.repos = make(map[string]*Repository, 0)
+	for _, fixRepo := range fixtureRepos {
+		s.repos[fixRepo.url] = NewPlainRepository()
+
+		d, err := os.Open(fixRepo.packfile)
+		c.Assert(err, IsNil)
+
+		r := packfile.NewReader(d)
+		r.Format = packfile.OFSDeltaFormat // TODO: how to know the format of a pack file ahead of time?
+
+		_, err = r.Read(s.repos[fixRepo.url].Storage)
+		c.Assert(err, IsNil)
+
+		c.Assert(d.Close(), IsNil)
+	}
+}
+
+func (s *SuiteTree) TestFile(c *C) {
+	for i, t := range []struct {
+		repo     string // the repo name as in localRepos
+		commit   string // the commit to search for the file
+		path     string // the path of the file to find
+		blobHash string // expected hash of the returned file
+		found    bool   // expected found value
+	}{
+		// use git ls-tree commit to get the hash of the blobs
+		{"https://github.com/tyba/git-fixture.git", "b029517f6300c2da0f4b651b8642506cd6aaf45d", "not-found",
+			"", false},
+		{"https://github.com/tyba/git-fixture.git", "b029517f6300c2da0f4b651b8642506cd6aaf45d", ".gitignore",
+			"32858aad3c383ed1ff0a0f9bdf231d54a00c9e88", true},
+		{"https://github.com/tyba/git-fixture.git", "b029517f6300c2da0f4b651b8642506cd6aaf45d", "LICENSE",
+			"c192bd6a24ea1ab01d78686e417c8bdc7c3d197f", true},
+
+		{"https://github.com/tyba/git-fixture.git", "6ecf0ef2c2dffb796033e5a02219af86ec6584e5", "not-found",
+			"", false},
+		{"https://github.com/tyba/git-fixture.git", "6ecf0ef2c2dffb796033e5a02219af86ec6584e5", ".gitignore",
+			"32858aad3c383ed1ff0a0f9bdf231d54a00c9e88", true},
+		{"https://github.com/tyba/git-fixture.git", "6ecf0ef2c2dffb796033e5a02219af86ec6584e5", "binary.jpg",
+			"d5c0f4ab811897cadf03aec358ae60d21f91c50d", true},
+		{"https://github.com/tyba/git-fixture.git", "6ecf0ef2c2dffb796033e5a02219af86ec6584e5", "LICENSE",
+			"c192bd6a24ea1ab01d78686e417c8bdc7c3d197f", true},
+
+		{"https://github.com/tyba/git-fixture.git", "35e85108805c84807bc66a02d91535e1e24b38b9", "binary.jpg",
+			"d5c0f4ab811897cadf03aec358ae60d21f91c50d", true},
+		{"https://github.com/tyba/git-fixture.git", "b029517f6300c2da0f4b651b8642506cd6aaf45d", "binary.jpg",
+			"", false},
+
+		{"https://github.com/tyba/git-fixture.git", "6ecf0ef2c2dffb796033e5a02219af86ec6584e5", "CHANGELOG",
+			"d3ff53e0564a9f87d8e84b6e28e5060e517008aa", true},
+		{"https://github.com/tyba/git-fixture.git", "1669dce138d9b841a518c64b10914d88f5e488ea", "CHANGELOG",
+			"d3ff53e0564a9f87d8e84b6e28e5060e517008aa", true},
+		{"https://github.com/tyba/git-fixture.git", "a5b8b09e2f8fcb0bb99d3ccb0958157b40890d69", "CHANGELOG",
+			"d3ff53e0564a9f87d8e84b6e28e5060e517008aa", true},
+		{"https://github.com/tyba/git-fixture.git", "35e85108805c84807bc66a02d91535e1e24b38b9", "CHANGELOG",
+			"d3ff53e0564a9f87d8e84b6e28e5060e517008aa", false},
+		{"https://github.com/tyba/git-fixture.git", "b8e471f58bcbca63b07bda20e428190409c2db47", "CHANGELOG",
+			"d3ff53e0564a9f87d8e84b6e28e5060e517008aa", true},
+		{"https://github.com/tyba/git-fixture.git", "b029517f6300c2da0f4b651b8642506cd6aaf45d", "CHANGELOG",
+			"d3ff53e0564a9f87d8e84b6e28e5060e517008aa", false},
+
+		// git submodule
+		{"https://github.com/cpcs499/Final_Pres_P.git", "70bade703ce556c2c7391a8065c45c943e8b6bc3", "Final",
+			"", false},
+		{"https://github.com/cpcs499/Final_Pres_P.git", "70bade703ce556c2c7391a8065c45c943e8b6bc3", "Final/not-found",
+			"", false},
+
+		{"https://github.com/jamesob/desk.git", "d4edaf0e8101fcea437ebd982d899fe2cc0f9f7b", "LICENSE",
+			"49c45e6cc893d6f5ebd5c9343fe4492360f339bf", true},
+		{"https://github.com/jamesob/desk.git", "d4edaf0e8101fcea437ebd982d899fe2cc0f9f7b", "examples",
+			"", false},
+		{"https://github.com/jamesob/desk.git", "d4edaf0e8101fcea437ebd982d899fe2cc0f9f7b", "examples/desk.sh",
+			"d9c7751138824cd2d539c23d5afe3f9d29836854", true},
+		{"https://github.com/jamesob/desk.git", "d4edaf0e8101fcea437ebd982d899fe2cc0f9f7b", "examples/not-found",
+			"", false},
+		{"https://github.com/jamesob/desk.git", "d4edaf0e8101fcea437ebd982d899fe2cc0f9f7b", "test/bashrc",
+			"e69de29bb2d1d6434b8b29ae775ad8c2e48c5391", true},
+		{"https://github.com/jamesob/desk.git", "d4edaf0e8101fcea437ebd982d899fe2cc0f9f7b", "test/not-found",
+			"", false},
+
+		{"https://github.com/spinnaker/spinnaker.git", "b32b2aecae2cfca4840dd480f8082da206a538da", "etc/apache2/sites-available/spinnaker.conf",
+			"1d452c616be4fb16d2cc6b8a7e7a2208a6e64d2d", true},
+
+		{"https://github.com/alcortesm/binary-relations.git", "c44b5176e99085c8fe36fa27b045590a7b9d34c9", "Makefile",
+			"2dd2ad8c14de6612ed15813679a6554bad99330b", true},
+		{"https://github.com/alcortesm/binary-relations.git", "c44b5176e99085c8fe36fa27b045590a7b9d34c9", "src/binrels",
+			"", false},
+		{"https://github.com/alcortesm/binary-relations.git", "c44b5176e99085c8fe36fa27b045590a7b9d34c9", "src/map-slice",
+			"", false},
+		{"https://github.com/alcortesm/binary-relations.git", "c44b5176e99085c8fe36fa27b045590a7b9d34c9", "src/map-slice/map-slice.go",
+			"12431e98381dd5097e1a19fe53429c72ef1f328e", true},
+		{"https://github.com/alcortesm/binary-relations.git", "c44b5176e99085c8fe36fa27b045590a7b9d34c9", "src/map-slice/map-slice.go/not-found",
+			"", false},
+	} {
+		commit, err := s.repos[t.repo].Commit(core.NewHash(t.commit))
+		c.Assert(err, IsNil, Commentf("subtest %d: %v (%s)", i, err, t.commit))
+
+		tree := commit.Tree()
+		file, err := tree.File(t.path)
+		found := err == nil
+		c.Assert(found, Equals, t.found, Commentf("subtest %d, path=%s, commit=%s", i, t.path, t.commit))
+		if found {
+			c.Assert(file.Hash.String(), Equals, t.blobHash, Commentf("subtest %d, commit=%s, path=%s", i, t.commit, t.path))
+		}
+	}
+}