I got to speak to the helpful Lee Saferite this weekend and he confirmed that a full upload would be helpful. Here’s what I did:
1. Created a new, empty subdomain on my server.
2. Uploaded the full 1.3.0 to it, after downloading and extracting that locally.
3. Pointed that to my live site’s database via local.xml
4. Hit the admin.
I got in. I then:
1. Backed up the live site and copied the new installation in.
2. Copied in my design theme and skin.
3. Copied in my own local code repository.
I had a dependency on Lee’s Modular Routers, so I just disabled that override via my app/etc XML file. I was then seeing my store as it should look for the most part.
I did server snapshot backups at each step and began reintroducing extensions. The only one I’ve had to leave out is Lee’s, which is still incompatible with 1.3.0. I’m awaiting some pointers on updating my code to take advantage of 1.3.0 functionality for custom controllers.
My problem was twofold:
1. When the upgrade happened, the first error I received was from Modular Routers. I didn’t correctly disable that or fully remove the dependency.
2. I either modified code in a search for a meaningful error, or the upgrade never fully ran. In either case, I was left with a botched 1.3.0 install.
Along the way I DID confirm that if you upgrade an extension with a Magento core module dependency stated, it WILL upgrade all of Magento. This seems ridiculous and destructive, and it was.
Fortunately my code was all modular - no core hacks - and I was able to complete the upgrade and restore all my custom work. Lesson learned: Backup before upgrading ANYTHING.