MINOR Upgrading notes around tab rewrites

docs/en/changelogs/3.0.0.md

@@ -326,7 +326,7 @@ The page tree moved from a bespoke tree library to [JSTree](http://jstree.com),
 which required changes to markup of the tree and its JavaScript architecture.
 This includes changes to `TreeDropdownField` and `TreeMultiSelectField`.
 
-### Settings-related fields move from `SiteTree->getCMSFields()` to new `SiteTree->getSettingsFields()` [getcmsfields]###
+### Settings-related fields move from SiteTree->getCMSFields() to new SiteTree->getSettingsFields() [getcmsfields]###
 
 The fields and tabs are now split into two separate forms, which required a structural
 change to the underlying class logic. In case you have added or removed fields
@@ -338,6 +338,41 @@ We've also removed the `$params` attribute on `DataObject->getCMSFields()`
 which could be used as a shortcut for customizations to `FormScaffolder`,
 in order to achieve E_STRICT compliance. Please use `FormScaffolder` directly.
 
+### Changed tab paths in SiteTree->getCMSFields() {#tab-paths}
+
+In order to simplify the interface, the `SiteTree->getCMSFields`
+method now only has one rather than two levels of tabs.
+This changes the tab paths, affecting any fields you might have added.
+We have also moved all fields from the "Metadata" tab into the "Main Content" tab. 
+
+	:::php
+	// 2.4
+	$fields->addFieldToTab('Root.Content.Main', $myField);
+	$fields->addFieldToTab('Root.Content.Metadata', $myOtherField);
+	// 3.0
+	$fields->addFieldToTab('Root.Main', $myField);
+	$fields->addFieldToTab('Root.Main', $myOtherField);
+
+![Tab paths in 2.4](_images/tab-paths-before.png)
+![Tab paths in 3.0](_images/tab-paths-after.png)
+
+The old paths are rewritten automatically, but will be deprecated in the next point release.
+If you are working with tab objects directly in your `FieldSet`, you'll need to update
+the tab names manually:
+
+	:::php
+	// 2.4
+	$fields->fieldByName('Root')->fieldByName('Content')->fieldByName('Main')->push($myField);
+	// 3.0
+	$fields->fieldByName('Root')->fieldByName('Main')->push($myField);
+
+If only a single tab is found in any CMS tabset, it is hidden by default
+to reduce UI clutter. You still need to address it through the usual tabset methods,
+as the underlying object structure doesn't change. Once you add more tabs,
+e.g. to the "Root.Main" tab in `SiteTree`, the tab bar automatically shows.
+
+![Tab paths in 3.0 with a custom tab](_images/tab-paths-customtab.png)
+
 ### New `SiteTree::$description` field to describe purpose of a page type [sitetree-description]###
 
 Please use this static property to describe the purpose of your page types,