No Manifest Destiny
The consumer of a package does not need to have a Package.swift
file, unless they will be establishing themselves as a package to be consumed elsewhere, or will be building from the command line. The Swift build system takes care of establishing the linkage to included packages.
In this entry, I will only cover the GUI methods, expressed by Xcode, as that is my experience with the SPM, and, I suspect, it will be the manner that most developers will interact with the Swift Package Manager.