dirstate: warn about non-explicitly rolledback parent-change

Now that the invalidation is dealt with by the context manager itself, we
should no longer need this in the unlocking code. We start with issuing a
warning if this is the case before actually dropping this code later.

mercurial/localrepo.py

@@ -3073,6 +3073,8 b' class localrepository:'
 
         def unlock():
             if self.dirstate.pendingparentchange():
+                msg = b"wlock release in the middle of a changing parents"
+                self.ui.develwarn(msg)
                 self.dirstate.invalidate()
             else:
                 self.dirstate.write(None)