git: correctly check for type of object when walking

hgext/git/manifest.py

@@ -168,7 +168,7 b' class gittreemanifest(object):'
         for te in tree:
             # TODO: can we prune dir walks with the matcher?
             realname = subdir + pycompat.fsencode(te.name)
-            if te.type == r'tree':
+            if te.type == pygit2.GIT_OBJ_TREE:
                 for inner in self._walkonetree(
                     self._git_repo[te.id], match, realname + b'/'
                 ):