storage: Add object type hint parameter to ObjectStorage.Get. (#69)

Some storage backends can optimize object lookup if they get
the object type that is expected. So we the signature of the Get
method is now Get(Hash, ObjectType).

Added generic tests for storage backends.

1 files changed, 10 insertions, 1 deletions

diff --git a/core/storage.go b/core/storage.go
index f3225d8..f3ec52b 100644
--- a/core/storage.go
+++ b/core/storage.go
@@ -9,7 +9,16 @@ var ErrStop = errors.New("stop iter")
 type ObjectStorage interface {
 	NewObject() Object
 	Set(Object) (Hash, error)
-	Get(Hash) (Object, error)
+	// Get an object by hash with the given ObjectType.
+	//
+	// Implementors should return (nil, core.ErrObjectNotFound) if an object
+	// doesn't exist with both the given hash and object type.
+	//
+	// Valid ObjectType values are CommitObject, BlobObject, TagObject, TreeObject
+	// and AnyObject.
+	//
+	// If AnyObject is given, the object must be looked up regardless of its type.
+	Get(Hash, ObjectType) (Object, error)
 	Iter(ObjectType) (ObjectIter, error)
 }