Allow increasing just tolerance in the boxfill phase

app/models/order_article.rb

@@ -223,17 +223,17 @@ def update_ordergroup_prices
 
  # Throws an exception when the changed article decreases the amount of filled boxes.
  def enforce_boxfill
- # Either nothing changes, or
- # missing_units becomes less and the amount doesn't decrease, or
+ # Either nothing changes, or the tolerance increases,
+ # missing_units decreases and the amount doesn't decrease, or
  # tolerance was moved to quantity. Only then are changes allowed in the boxfill phase.
  delta_q = quantity - quantity_was
  delta_t = tolerance - tolerance_was
  delta_mis = missing_units - missing_units_was
  delta_box = units_to_order - units_to_order_was
- unless (delta_q == 0 && delta_t == 0) ||
+ unless (delta_q == 0 && delta_t >= 0) ||
  (delta_mis < 0 && delta_box >= 0 && delta_t >= 0) ||
  (delta_q > 0 && delta_q == -delta_t)
- raise ActiveRecord::RecordNotSaved.new("Change not acceptable in boxfill phase, sorry.", self)
+ raise ActiveRecord::RecordNotSaved.new("Change not acceptable in boxfill phase for '#{article.name}', sorry.", self)
  end
  end