Page history should support some kind of branching, perhaps by allowing a special log entry that says "at this revision there was a merge/split with that revision".
Possibly the log entry should also be able to refer to a global site id (ref global site ids in Wikidata) so it is possible to do proper attribution.
The log entries could be made automatically during editing, or added afterwards by an admin through a special page.
Version: 1.21.x
Severity: enhancement
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=38664