Hey Isaac!
This is a fine place for feedback :)
The ability to revert and/or transfer builds from one channel to another has been requested a few times, and it's definitely on my TODO list.
There's a few things I need to finish up in order to make it available though: for example, when a user has already upgraded to a build, and it's rolled back, I'd like to avoid a full re-downloaded. Generating a reverse patch seems like overkill, but I've had a block system in the works that would allow moving an install to any build with minimal downloads.
So my roadmap for butler looks like this:
- Iron out the last few corner cases with the current feature-set
- Release app version with experimental "extract while downloading" feature
- Roll out blocks-based downloads for all butler builds, release app version with that feature, opt-in
- Allow setting a channel to any build (would probably implemented as: the backend fetches the previous build and the one you want to set it to, and does its own diff).
Somewhere in that timeline also fits bsdiff integration, which I've been working on, and which makes patches even smaller (it's a post-processing step after the initial patch creation while pushing).
I realize that answer covers a lot more than you asked for, but I hope it gives you a view of what we're currently up to!