Current a test for a channel update PR sends requests to the packagecontrol.io website. We cannot update the logic that runs there and it's flaky and outdated.
There are new actions that could replace most of what it does. The LSP project uses them. They're probably already overly complex and a bit outdated, but it's a good starting point.
The most important things are guarding validity agains the schema for all changes, and making sure new package additions don't cause problems that aren't easy to spot manually.
It is not a goal to add comments to the PR's or to add a reviewer bot or anything. Scripts that output to stdout would be fine.
For the time being an additional constraint is that we don't have access to the package_control_channel to add for instance secrets.