According to @Dereckson in T156395#2974782 /source/mediawiki/browse/master/maintenance/reassignEdits.php hasn't received much attention since a lot of years. Given that global user merge is not yet possible (T49918), having this script updated not to migrate only edits but to also migrate logs, etc. would be a good idea for some carefully selected cases where this could be used. I wonder if some maintenance and updating could be done in such script to accomplish that since MediaWiki-extensions-UserMerge is not very safe. Thanks.