rebase: only change self.state when collapsing in _finishrebase

When the code executes to _finishrebase, self.state should be populated with
correct destinations and do not need to be written to a node. The code was
introduced by 8dc45c9059, which seems to avoid setting state values to None
but it didn't provide more details.

Differential Revision: https://phab.mercurial-scm.org/D346

hgext/rebase.py

@@ -461,12 +461,10 b' class rebaseruntime(object):'
                                        editor=editor,
                                        keepbranches=self.keepbranchesf,
                                        date=self.date)
-            if newnode is None:
-                newrev = self.dest
-            else:
+            if newnode is not None:
                 newrev = repo[newnode].rev()
-            for oldrev in self.state.iterkeys():
-                self.state[oldrev] = newrev
+                for oldrev in self.state.iterkeys():
+                    self.state[oldrev] = newrev
 
         if 'qtip' in repo.tags():
             updatemq(repo, self.state, self.skipped, **opts)