We mirror the source code on GitLab. We put the upstream 17 code in the 17-base branch and our code on top of it in the 17 branch:
https://gitlab.com/grapheneos/kernel_pixel/-/tree/17-base
https://gitlab.com/grapheneos/kernel_pixel_muzel/-/tree/17-b...
We also have mirrors of the QPR1 Beta and QPR2 Beta code there too.