Every tiny shader update would require the user to re-download the package (and crosire to repack it). That way you can just reinstall ReShade to get the latest effects. And remember, ReShade is only the injector, the shaders are just a sample set. People still assume ReShade and the Framework that got shipped along with 1.X versions are one and the same thing.
Just what I said. ReShade =/= the repo. The shaders are only an example, hence the installer downloads them, not ReShade. Hence ReShade itself isn't bound to the shaders in the repo.
What could be done maybe is supporting something in shader code like a pragma that supplies a URL to check for each shader individually so new shaders would need their own repositories on any site. So like MXAO would have an entry to re-download it from the github repo, a different shader maybe to fetch updates from some FTP server. But there are more important things to be done by far.