Merge pull request #6503 from vzabaznov/patch-5

Update private-content.md

Author: dobooth

src/guides/v2.3/extension-dev-guide/cache/page-caching/private-content.md

@@ -100,6 +100,26 @@ The following example adds comments to [app/code/Magento/Catalog/etc/frontend/se
 </config>
 ```
 
+There are sections that allow you to declare an 'action' node without specifying a sections, for instance, when logging out:
+
+```xml
+<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Customer:etc/sections.xsd">
+  <action name="customer/account/logout"/>
+</config>
+```
+
+This tells Magento to invalidate all sections. But if you have declared sections for this action in another .xml file, it will override the initial sections and only newly added sections will be invalidated. If you need to reload all sections on some action, use `*` as section name or use an empty action and ensure that they will not be overriden by any other rules:
+
+```xml
+<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+        xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Customer:etc/sections.xsd">
+    <action name="customer/account/editPost">
+        <section name="*"/>
+    </action>
+</config>
+```
+
 {:.bs-callout-warning}
 Use only HTTP POST or PUT methods to change state (e.g., adding to a shopping cart, adding to a wishlist, etc.) and do not expect to see caching on these methods. Using GET or HEAD methods might trigger caching and prevent updates to private content. For more information about caching, see [RFC-2616 section 13](https://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html){:target="_blank"}.