When there are a detected edit conflict it is possible to use the base revision (or a later stored field-specific revision) to generate a diff and then patch the latest revision with an appropriate applicable diff.
This attempt on patching the entity can be done before or after the collision detection in "userWasLastToEdit". If the patching is done after the collision detection it should probably be done early in ApiModifyItem (and similar), probably before it is necessary to make the decision on which revision to modify.
Version: unspecified
Severity: normal
Whiteboard: storypoints: 5
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=37685