overlwayworkingctx: remove doubly bad reference to wrapped ctx for copies

`_wrappedctx` lives on overlwayworkingctx, not on the repo object, so
we should access it as `._wrappedctx`, not `._repo._wrappedctx`. More
importantly, the overlayworkingctx is relative to its base, not
including it, so the copies returned should not include copies made in
the base.

Differential Revision: https://phab.mercurial-scm.org/D7801

mercurial/context.py

@@ -2224,7 +2224,7 b' class overlayworkingctx(committablectx):'
         ]
 
     def p1copies(self):
-        copies = self._repo._wrappedctx.p1copies().copy()
+        copies = {}
         narrowmatch = self._repo.narrowmatch()
         for f in self._cache.keys():
             if not narrowmatch(f):
@@ -2236,7 +2236,7 b' class overlayworkingctx(committablectx):'
         return copies
 
     def p2copies(self):
-        copies = self._repo._wrappedctx.p2copies().copy()
+        copies = {}
         narrowmatch = self._repo.narrowmatch()
         for f in self._cache.keys():
             if not narrowmatch(f):