Fix：3343 【礼品】购买礼品数量，增加可以手动输入数字

mixins/goCartMixins.js

@@ -276,7 +276,11 @@ export default {
       let stock = productSelect.stock || 0
       let num = this.attr.productSelect
       if (changeValue) {
-        num.cart_num++
+        if(changeValue > 1) {
+          num.cart_num = changeValue
+        } else {
+          num.cart_num++
+        }
         if (num.cart_num > stock) {
           if(stock < 1) {
             this.$set(this.attr.productSelect, 'cart_num', 1)
@@ -291,7 +295,7 @@ export default {
             this.$set(this, 'cart_num', 1)
           } else {
             this.$set(this.attr.productSelect, 'cart_num', num.cart_num)
-            this.$set(this, 'cart_num', num.cart_num)
+            // this.$set(this, 'cart_num', num.cart_num)
           }
         }
       } else {