update git_object to be the more correct oid

Author: jeremywestwood

pygit2/packbuilder.py

@@ -53,19 +53,19 @@ def __len__(self):
         return C.git_packbuilder_object_count(self._packbuilder)
 
     @staticmethod
-    def convert_object_to_oid(git_object):
-        oid = ffi.new('git_oid *')
-        ffi.buffer(oid)[:] = git_object.raw[:]
-        return oid
-
-    def add(self, git_object):
-        oid = self.convert_object_to_oid(git_object)
-        err = C.git_packbuilder_insert(self._packbuilder, oid, ffi.NULL)
+    def convert_object_to_oid(oid):
+        git_oid = ffi.new('git_oid *')
+        ffi.buffer(git_oid)[:] = oid.raw[:]
+        return git_oid
+
+    def add(self, oid):
+        git_oid = self.convert_object_to_oid(oid)
+        err = C.git_packbuilder_insert(self._packbuilder, git_oid, ffi.NULL)
         check_error(err)
 
-    def add_recur(self, git_object):
-        oid = self.convert_object_to_oid(git_object)
-        err = C.git_packbuilder_insert_recur(self._packbuilder, oid, ffi.NULL)
+    def add_recur(self, oid):
+        git_oid = self.convert_object_to_oid(oid)
+        err = C.git_packbuilder_insert_recur(self._packbuilder, git_oid, ffi.NULL)
         check_error(err)
 
     def set_threads(self, n_threads):