https://gerrit.wikimedia.org/r/17829

That should do it for now, but if I've missed part of the problem here, I can easily do something more.

Basically, anywhere there's a TemplateRequest, I've checked for an oldid query string parameter, and used it in the relevant API call. This only happens in GET requests right now, and it might not necessarily get the old versions of templates, etc., that were in use at the time. I can change both of those things, I think, with some small pointers to where the changes are necessary.

Mass-moving bugs into the new 'Parsoid' product.

Works nicely for GET requests, and should also be used by the VE for POST requests. We don't use the oldid on POST yet, but will likely do so in the future for reconciliation and possibly retrieval of rt info.