I wonder if using long lived branches for specialized features would make sense for Pyodide.

For instance, we can't use threading #237 until all major browsers support it. At the same some people might want to experiment with it already now. So ideally we could have a build with threading and a build without. Doing both in our CI would be complex (and resource intensive) while I think having a separate upstream threading branch that would deploy to cdn.jsdelivr.net/pyodide/dev/threading/ should be more manageable. What's a bit non obvious there is now to sync releases from different branches, if we make them (maybe tag as v0.19.0-threading for instance?) but this could be solved once we get there.

Other things that I wouldn't mind deploying on a separate branch is builds without fpcast (#1677). If people start using this, without it being the main deployment, I think we would feel more confident with integrating it into main.

Also maybe another feature branch for a very minimal Pyodide build, with a smallest size imprint we can manage. Ideally size optimizations should be opt-in in the main branch, bit I'm not sure all could be. cc @phorward

Of course having too many of those, would require more work on syncing them and resolving conflicts. But maybe we could find some middle ground.