A lot of these packages have Arch-specific modifications. For example, filesystem doesn’t even have a non-Arch upstream as it defines the filesystem layout. That PKGBUILD and everything it depends on is the Arch source. Distributions are defined by which packages they include.
Cheers! It looks like this is then the PKGBUILD
https://gitlab.archlinux.org/archlinux/packaging/packages/base/-/blob/main/PKGBUILD?ref_type=heads
In which case, there are no packages defined there which are Arch specific except pacman. So… pacman is the Arch source, right?
A lot of these packages have Arch-specific modifications. For example, filesystem doesn’t even have a non-Arch upstream as it defines the filesystem layout. That PKGBUILD and everything it depends on is the Arch source. Distributions are defined by which packages they include.