pub fn all_direct_deps(&self) -> [(BuildPlatform, &PackageSet<'g>); 2] {
        [
            (BuildPlatform::Target, self.target_direct_deps()),
            (BuildPlatform::Host, self.host_direct_deps()),
        ]
    }
Returns the set of workspace and direct dependency packages across the target and host
build platforms.
guppy/src/graph/cargo/cargo_api.rs