shelve: use cg?unpacker.apply() instead of changegroup.addchangegroup()

hgext/shelve.py

@@ -96,7 +96,7 class shelvedfile(object):
         fp = self.opener()
         try:
             gen = exchange.readbundle(self.repo.ui, fp, self.fname, self.vfs)
-            changegroup.addchangegroup(self.repo, gen, 'unshelve',
+            gen.apply(self.repo, 'unshelve',
                                        'bundle:' + self.vfs.join(self.fname),
                                        targetphase=phases.secret)
         finally: