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.
https://archlinux.org/packages/core/any/base/
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.