message: add runtime log
diff: @@ -122,6 +122,8 @@ where
  /// Increments the current revision counter and returns the new value.
  pub(crate) fn increment_revision(&self) -> Revision {
  + log::debug!("increment_revision()");
  +
  if !self.local_state.borrow().query_stack.is_empty() {
  panic!("increment_revision invoked during a query computation");
  }
  @@ -230,6 +232,8 @@ where
  /// Obviously, this should be user configurable at some point.
  pub(crate) fn report_unexpected_cycle(&self, descriptor: DB::QueryDescriptor) -> ! {
  + debug!("report_unexpected_cycle(descriptor={:?})", descriptor);
  +
  let local_state = self.local_state.borrow();
  let LocalState { query_stack, .. } = &*local_state;
  