stock-logistics-warehouse/stock_reserve/view/product.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data noupdate="0">

        <record model="ir.ui.view" id="product_form_view">
            <field name="name">product.product.form.reserve</field>
            <field name="model">product.product</field>
            <field name="inherit_id" ref="procurement.product_form_view_procurement_button"/>
            <field name="arch" type="xml">
                <xpath expr="//div[@name='buttons']" position="inside">
                    <button string="Stock Reservations"
                        name="open_stock_reservation"
                        type="object"/>
                </xpath>
            </field>
        </record>

    </data>
</openerp>