Return the same index and odb objects in successive calls

Instead of creating a new Go object each time Repository.Index()/Odb()
are called, return the same one as long as the underlying pointer
remains the same.

index_test.go

@@ -22,6 +22,20 @@ func TestCreateRepoAndStage(t *testing.T) {
 	}
 }
 
+func TestIndexTwoCalls(t *testing.T) {
+	repo := createTestRepo(t)
+	defer os.RemoveAll(repo.Workdir())
+
+	idx1, err := repo.Index()
+	checkFatal(t, err)
+	idx2, err := repo.Index()
+	checkFatal(t, err)
+
+	if idx1 != idx2 {
+		t.Fatal("Two Index() calls give different objects")
+	}
+}
+
 func checkFatal(t *testing.T, err error) {
 	if err == nil {
 		return

odb.go

@@ -17,6 +17,12 @@ type Odb struct {
 	ptr *C.git_odb
 }
 
+func newOdbFromC(ptr *C.git_odb) *Odb {
+	odb := &Odb{ptr}
+	runtime.SetFinalizer(odb, (*Odb).Free)
+	return odb
+}
+
 func (v *Odb) Exists(oid *Oid) bool {
 	ret := C.git_odb_exists(v.ptr, oid.toC())
 	return ret != 0

odb_test.go

@@ -33,3 +33,17 @@ func TestOdbStream(t *testing.T) {
 		t.Fatal("Wrong data written")
 	}
 }
+
+func TestOdbTwoCalls(t *testing.T) {
+	repo := createTestRepo(t)
+	defer os.RemoveAll(repo.Workdir())
+
+	odb1, err := repo.Odb()
+	checkFatal(t, err)
+	odb2, err := repo.Odb()
+	checkFatal(t, err)
+
+	if odb1 != odb2 {
+		t.Fatal("Two Odb() calls return different objects")
+	}
+}

repository.go

@@ -13,6 +13,11 @@ import (
 // Repository
 type Repository struct {
 	ptr *C.git_repository
+
+	// These are kept so that two repo.Index() or repo.Odb() calls
+	// return the same object, as we do in the library
+	idx *Index
+	odb *Odb
 }
 
 func OpenRepository(path string) (*Repository, error) {
@@ -72,17 +77,22 @@ func (v *Repository) Config() (*Config, error) {
 }
 
 func (v *Repository) Index() (*Index, error) {
-	var ptr *C.git_index
-
 	runtime.LockOSThread()
 	defer runtime.UnlockOSThread()
 
+	var ptr *C.git_index
 	ret := C.git_repository_index(&ptr, v.ptr)
 	if ret < 0 {
 		return nil, LastError()
 	}
 
-	return newIndexFromC(ptr), nil
+	if v.idx != nil && v.idx.ptr == ptr {
+		C.git_index_free(ptr) // decrease the refcount
+		return v.idx, nil
+	}
+
+	v.idx = newIndexFromC(ptr)
+	return v.idx, nil
 }
 
 func (v *Repository) lookupType(oid *Oid, t ObjectType) (Object, error) {
@@ -246,18 +256,23 @@ func (v *Odb) Free() {
 	C.git_odb_free(v.ptr)
 }
 
-func (v *Repository) Odb() (odb *Odb, err error) {
-	odb = new(Odb)
-
+func (v *Repository) Odb() (*Odb, error) {
 	runtime.LockOSThread()
 	defer runtime.UnlockOSThread()
 
-	if ret := C.git_repository_odb(&odb.ptr, v.ptr); ret < 0 {
+	var ptr *C.git_odb
+	if ret := C.git_repository_odb(&ptr, v.ptr); ret < 0 {
 		return nil, LastError()
 	}
 
-	runtime.SetFinalizer(odb, (*Odb).Free)
-	return
+	if v.odb != nil && v.odb.ptr == ptr {
+		C.git_odb_free(ptr) // decrease the refcount
+		return v.odb, nil
+	}
+
+
+	v.odb = newOdbFromC(ptr)
+	return v.odb, nil
 }
 
 func (repo *Repository) Path() string {

submodule.go

@@ -153,7 +153,7 @@ func (sub *Submodule) Save() error {
 func (sub *Submodule) Owner() *Repository {
 	repo := C.git_submodule_owner(sub.ptr)
 	//FIXME: how to handle dangling references ?
-	return &Repository{repo}
+	return &Repository{ptr: repo}
 }
 
 func (sub *Submodule) Name() string {