Reference/Release Notes/2.93/Core

Resync Process Improvements
Resyncing a library override is needed when the source linked data gets changes in the relationships between its data-blocks.

This process has been made way easier, and most of the time fully automatic:
 * With newly created files/overrides, needed resync are detected and performed automatically when loading the .blend file.
 * However, in some cases, especially with older files that were saved with 'broken' (non-hierarchy-matching) overrides, resync itself cannot rebuild properly the override as expected (some objects might go missing e.g.). For that case, a new operation in the Outliner right-click menu was added, `Resync Library Override Hierarchy Enforce`, that essentially performs a more aggressive resync, at the cost of a potential loss of some overrides on ID pointers properties.
 * An option (under `Experimental` area of user Preferences) was also added to allow disabling this auto-resync feature on load, since some complex production files may need proper manual processing first.

Auto-resync detects and keeps around data-blocks no more needed by the override, but that were previously edited by the user, and for objects or collections, it put them in a dedicated collection, `OVERRIDE_RESYNC_LEFTOVERS`.

New Override View in the Outliner
A basic informative view of current library overrides has been added to the outliner.



System-generated overrides (like the overrides of pointers to other override data-blocks which ensures the override hierarchy) are hidden by default, and can be shown through a filter option.

Potential info or warning messages from (auto-)resync process are also shown, as an icon + tooltip next to the affected items.

Blenloader

 * Added support for using memory-mapped IO in order to speed up uncompressed .blend file loading.

Data Management

 * The Purge operator to delete unused data-blocks has been improved, it can now operate on only linked or local data, and can recursively delete all 'indirectly' unused data-blocks at once ( and related). new behavior only exposed from `File -> Clean Up` menu currently.

Linked Data

 * Missing libraries and linked data-blocks now are reported as a single warning in the UI when loading a .blend file with broken libraries. Full info remains available in the console or Info editor.