3 files changed, 22 insertions, 9 deletions
diff --git a/internal/hash.go b/internal/hash.go
index db55b24..0540db1 100644
--- a/internal/hash.go
+++ b/internal/hash.go
@@ -30,6 +30,11 @@ func NewHash(s string) Hash {
 	return h
 }
 
+func (h Hash) IsZero() bool {
+	var empty Hash
+	return h == empty
+}
+
 func (h Hash) String() string {
 	return hex.EncodeToString(h[:])
 }
diff --git a/internal/hash_test.go b/internal/hash_test.go
index 222f3b4..063bd23 100644
--- a/internal/hash_test.go
+++ b/internal/hash_test.go
@@ -25,3 +25,11 @@ func (s *HashSuite) TestNewHash(c *C) {
 
 	c.Assert(hash, Equals, NewHash(hash.String()))
 }
+
+func (s *HashSuite) TestIsZero(c *C) {
+	hash := NewHash("foo")
+	c.Assert(hash.IsZero(), Equals, true)
+
+	hash = NewHash("8ab686eafeb1f44702738c8b0f24f2567c36da6d")
+	c.Assert(hash.IsZero(), Equals, false)
+}
diff --git a/internal/object.go b/internal/object.go
index 0f11140..a30bc9d 100644
--- a/internal/object.go
+++ b/internal/object.go
@@ -71,18 +71,18 @@ func (o *RAWObject) Write(p []byte) (n int, err error) {
 }
 
 type RAWObjectStorage struct {
-	Objects map[Hash]*RAWObject
-	Commits map[Hash]*RAWObject
-	Trees   map[Hash]*RAWObject
-	Blobs   map[Hash]*RAWObject
+	Objects map[Hash]Object
+	Commits map[Hash]Object
+	Trees   map[Hash]Object
+	Blobs   map[Hash]Object
 }
 
 func NewRAWObjectStorage() *RAWObjectStorage {
 	return &RAWObjectStorage{
-		Objects: make(map[Hash]*RAWObject, 0),
-		Commits: make(map[Hash]*RAWObject, 0),
-		Trees:   make(map[Hash]*RAWObject, 0),
-		Blobs:   make(map[Hash]*RAWObject, 0),
+		Objects: make(map[Hash]Object, 0),
+		Commits: make(map[Hash]Object, 0),
+		Trees:   make(map[Hash]Object, 0),
+		Blobs:   make(map[Hash]Object, 0),
 	}
 }
 
@@ -92,7 +92,7 @@ func (o *RAWObjectStorage) New() Object {
 
 func (o *RAWObjectStorage) Set(obj Object) Hash {
 	h := obj.Hash()
-	o.Objects[h] = obj.(*RAWObject)
+	o.Objects[h] = obj
 
 	switch obj.Type() {
 	case CommitObject: