Ask HN: Any open source alternatives to Sparkle or Squirrel for Mac app updates?

Looking for something that is less opinionated, ideally written in Swift, and that doesn't provide its own UI. I'm a big fan of go-update ^1 for Go apps. It's stupid simple and easy to integrate with an update API since it doesn't care about anything except being passed an update and a signature. Know of anybody working on something like that for Mac apps? ^1: https://github.com/inconshreveable/go-update