Maintenance script that merges the revision_actor_temp table into the revision table.

It will run automatically during the upgrade to MediaWiki 1.39.

On large wikis, you can set $wgActorTableSchemaMigrationStage to SCHEMA_COMPAT_WRITE_TEMP_AND_NEW | SCHEMA_COMPAT_READ_TEMP prior to the upgrade to MediaWiki 1.39 (the config was completely removed in 1.39.0) and run this script to populate the new schema.