### Image renditions can now be prefetched by filter
When using a queryset to render a list of images, you can now use the ``prefetch_renditions()`` queryset method to prefetch the renditions needed for rendering with a single extra query, similar to ``prefetch_related``. If you have many renditions per image, you can also call it with filters as arguments - ``prefetch_renditions("fill-700x586", "min-600x400")`` - to fetch only the renditions you intend on using for a smaller query. For long lists of images, this can provide a significant boost to performance. See [](prefetching_image_renditions) for more examples. This feature was developed by Tidiane Dia and Karl Hobley.
* Convert various pages in the documentation to Markdown (Khanh Hoang, Vu Pham, Daniel Kirkham, LB (Ben) Johnston, Thiago Costa de Souza, Benedict Faw, Noble Mittal, Sævar Öfjörð Magnússon)
* Use `FormData` instead of jQuery's `form.serialize` when editing documents or images just added so that additional fields can be better supported (Stefan Hammer)
* Add informational Codecov status checks for GitHub CI pipelines (Tom Hu)
* Introduce JavaScript chooser module, including a SearchController class which encapsulates the standard pattern of re-rendering the results panel in response to search queries and pagination (Matt Westcott)
* Upgrade notification, shown to admins on the dashboard if Wagtail is out of date, will now link to the release notes for the closest minor branch instead of the latest patch (Tibor Leupold)
* Upgrade notification can now be configured to only show updates when there is a new LTS available via `WAGTAIL_ENABLE_UPDATE_CHECK = 'lts'` (Tibor Leupold)
* Adopt new breadcrumbs on the page explorer (listing) view and the page chooser modal, remove legacy breadcrumbs code for move page as no longer used (Paarth Agarwal)
* Ensure `aria-label` is not set on locale selection dropdown within page chooser modal as it was a duplicate of the button contents (LB (Ben Johnston))
* Revise the `ModelAdmin` title column behaviour to only link to 'edit' if the user has the correct permissions, fallback to the 'inspect' view or a non-clickable title if needed (Stefan Hammer)
### `base_url_path` keyword argument added to AdminURLHelper
The `wagtail.contrib.modeladmin.helpers.AdminURLHelper` class now accepts a `base_url_path` keyword argument on its constructor. Custom subclasses of this class should be updated to accept this keyword argument.
Safari 13 will no longer be officially supported as of this release, this deviates the current support for the last 3 version of Safari by a few months and was required to add better support for RTL languages.
The `PageRevision` model has been replaced with a generic `Revision` model. If you use the `PageRevision` model in your code, make sure that:
* Creation of `PageRevision` objects should be updated to create `Revision` objects using the page's `id` as the `object_id`, the default `Page` model's content type as the `base_content_type`, and the page's specific content type as the `content_type`.
* Queries that use the `PageRevision.objects` manager should be updated to use the `Revision.page_revisions` manager.
*`Revision` queries that use `Page.id` should be updated to cast the `Page.id` to a string before using it in the query (e.g. by using `str()` or `Cast("page_id", output_field=CharField())`).
*`Page` queries that use `PageRevision.page_id` should be updated to cast the `Revision.object_id` to an integer before using it in the query (e.g. by using `int()` or `Cast("object_id", output_field=IntegerField())`).
* Access to `PageRevision.page` should be updated to `Revision.content_object`.
If you maintain a package across multiple Wagtail versions that includes a model with a `ForeignKey` to the `PageRevision` model, you can create a helper function to correctly resolve the model depending on the installed Wagtail version, for example:
### `Page.get_latest_revision_as_page` renamed to `Page.get_latest_revision_as_object`
The `Page.get_latest_revision_as_page` method has been renamed to `Page.get_latest_revision_as_object`. The old name still exists for backwards-compatibility, but calling it will raise a `RemovedInWagtail50Warning`.
Custom choosers should no longer use `wagtail.admin.widgets.chooser.AdminChooser` which has been replaced with `wagtail.admin.widgets.chooser.BaseChooser`.
### `explorer_breadcrumb` template tag has been renamed to `breadcrumbs`, `move_breadcrumb` has been removed
The `explorer_breadcrumb` template tag is not documented, however if used it will need to be renamed to `breadcrumbs` and the `url_name` is now a required arg.
The `move_breadcrumb` template tag is no longer used and has been removed.
