[IMP] Changing product qty on product form should work with serial numbers...

[IMP] Changing product qty on product form should work with serial numbers like in 7.0, but we should explain it
Closes #3984

addons/stock/wizard/stock_change_product_qty.py

@@ -98,7 +98,7 @@ class stock_change_product_qty(osv.osv_memory):
                 'product_id': data.product_id.id,
                 'location_id': data.location_id.id,
                 'lot_id': data.lot_id.id}, context=context)
-            product = data.product_id.with_context(location=data.location_id.id)
+            product = data.product_id.with_context(location=data.location_id.id, lot_id= data.lot_id.id)
             th_qty = product.qty_available
             line_data = {
                 'inventory_id': inventory_id,

addons/stock/wizard/stock_change_product_qty_view.xml

@@ -10,7 +10,11 @@
                         <field name="new_quantity" />
                         <field name="product_id" invisible="1"/>
                         <field name="location_id" groups="stock.group_locations"/>
-                        <field name="lot_id"  context="{'search_default_product_id':product_id,'default_product_id':product_id}" groups="base.group_no_one"/>
+                        <field name="lot_id"  context="{'search_default_product_id':product_id,'default_product_id':product_id}" groups="stock.group_production_lot"/>
+                        <p groups="stock.group_production_lot" class="oe_grey">
+                            When you select a serial number (lot), the quantity is corrected with respect to
+                            the quantity of that serial number (lot) and not to the total quantity of the product.
+                        </p>
                     </group>
                     <footer>
                         <button name="change_product_qty" string="_Apply" type="object" class="oe_highlight"/>