Old bugs and such may have left the archive table with multiple rows
using the same ar_rev_id, or rows that also exist in the revision table.
These need to be cleaned up for MCR.
The maintenance script added here will delete rows that appear to be
duplicates of the same change, and will assign new IDs to rows that do
not appear to be duplicates.
Bug: T193180
Change-Id: I39b0825c9469e074ded3df33a4f06a1ef0edb494
Revisions deleted before MediaWiki 1.5 do not have a value in this
field. This is going to be a problem for migration to the MCR schema, so
provide a maintenance script to clean this up.
Then, for good measure, change the schema to make the field
non-nullable.
Bug: T182678
Change-Id: Ie2e11f12a30f379db32c3e074658012c6f93adb0
