How can I use the latest version of SDL2?

[km19809]

When I trying to link SDL, Emscripten fetches:
ports:INFO: retrieving port: sdl2 from https://github.com/libsdl-org/SDL/archive/release-2.0.20.zip
However, the latest version is 2.0.22.

Actually, what I want is to use the pre-release version, but I could not find out how to use it instead of 2.0.20.
Can I modify something or wait until the emscripten update?

[kripken]

You can modify tools/ports/sdl2.py to tell it to use a different hash/commit. See TAG and HASH near the top.