I spent some time playing around GitHub api, and results a small tool,
I didn't implement it in uscan. But it can work well with uscan.
A demo service is at https://watch.zhsj.me/
Take one of packages I maintained,
https://watch.zhsj.me/github/xiaq/persistent is the watch url.
And the following d/watch works fine,
This tool works both as web service and cli.
I hope you find this tool useful.