repo-or-peer: deprecate calling `islocal` on non-path object

There object have a `.local()` method and should use it.

mercurial/hg.py

@@ -168,6 +168,7 b' def islocal(repo):'
             return _peerlookup(repo).islocal(repo)
         except AttributeError:
             return False
+    repo.ui.deprecwarn(b"use obj.local() instead of islocal(obj)", b"6.4")
     return repo.local()