Maintain the original reference when splitting shipments and productions

Closes #14190
(grafted from b1d2fd68d7e2b865675d7d466e8874247c76c786)

--HG--
branch : 6.0

modules/production_split/production.py

@@ -48,6 +48,7 @@ class Production(metaclass=PoolMeta):
         while (remainder > quantity
                 and (count or count is None)):
             productions.extend(self.copy([self], {
+                        'reference': lambda data: data['reference'],
                         'quantity': quantity,
                         'uom': uom.id,
                         'inputs': None,

modules/stock_split/stock.py

@@ -193,7 +193,12 @@ class SplitShipment(Wizard):
             Move.delete(
                 [m for m in shipment.inventory_moves if m.state == 'draft'])
 
-        shipment, = Shipment.copy([shipment], default={'moves': None})
+        shipment, = Shipment.copy(
+            [shipment],
+            default={
+                'reference': lambda data: data['reference'],
+                'moves': None,
+                })
         Move.write(list(self.start.moves), {'shipment': str(shipment)})
         return 'end'