Fix free shipping logic in Magento 2.1.10 - See https://github.com/magento/magento2/issues/12573#issuecomment-352926916

fix-free-shipping-cart-price-rule.patch

Index: Model/SalesRule/Calculator.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- Model/SalesRule/Calculator.php	(date 1513354238000)
+++ Model/SalesRule/Calculator.php	(date 1513354238000)
@@ -45,6 +45,17 @@
                     break;
 
                 case Rule::FREE_SHIPPING_ADDRESS:
+                    // Begin edit
+                    /**
+                     * SMC-490_192 - Fix a bug where the "Free Shipping" payment method never shows up
+                     *
+                     * This is how it's *supposed* to work (2.1.6): http://take.ms/b8hfy
+                     * Reproduced this issue in a 2.1.9 EE and 2.1.10 EE install with sample data: http://take.ms/CwfKS
+                     *
+                     * Adding this one line works around the issue
+                     */
+                    $item->setFreeShipping($rule->getDiscountQty() ? $rule->getDiscountQty() : true);
+                    // End edit
                     $address->setFreeShipping(true);
                     break;
             }