Create 8.x upgrade rules

So I'm porting a silly module from D7 to D8 for my DrupalCon Sydney presentation and thought it might be useful to start making a list of things I hit as I go through, or even try and write a couple of simple ones to get the ball rolling.

I'm a little confused though what the path looks like for Coder Upgrade 8.x rules. Here's what I've managed to figure out:

1) I found some documentation for Coder Upgrade, including how to write your own upgrade routine.

2) However, all the upgrade routines under coder_upgrade/conversions are at the top level, and they appear to assume that they'll only ever be running for 6.x to 7.x modules. I don't see an easy way to toss 8.x routines in there as well.

3) I noticed that amitgoyai posted #1816302: Code Review 7.x-1.2 to 8.x-1.x Patch which ports Coder Review to Drupal 8. I could do something similar for Coder Upgrade, but given all the various dependencies (e.g. grammar parser) and the fact that they'd have to be upgraded to D8 too, this seems like not the best use of time right now. Maybe after code freeze.

4) There's also a parallel effort going on in coder_sniffer module to make things "sniffs" from PHPCS. I looked under that directory structure too, but there doesn't seem to be anything about upgrade routines in there. Should there be? If so, where are the docs for writing sniffs?

Any help would be appreciated. :)

So http://dupgrade.com/ exists, and apparently has D7 => D8 rules already, although these are not in the Git repo anywhere that I can find. And according to http://dupgrade.com/tools/php/pricing I imagine this is intentional. Hm.