dirstate: replace `_add` call in `setparent`

Same logic as the previous changeset, it get us closer to removed older API on
the dirstate.

Differential Revision: https://phab.mercurial-scm.org/D11425

mercurial/dirstate.py

@@ -409,7 +409,13 b' class dirstate(object):'
                     source = self._map.copymap.get(f)
                     if source:
                         copies[f] = source
-                    self._add(f)
+                    self._check_new_tracked_filename(f)
+                    self._updatedfiles.add(f)
+                    self._map.reset_state(
+                        f,
+                        p1_tracked=False,
+                        wc_tracked=True,
+                    )
         return copies
 
     def setbranch(self, branch):