It's honestly a bit baffling that this functionality was not included with storyboards in the first place. Not always the best solution, but it's certainly nice to have.
Apple started shipping the Xcode betas in a new archive file format, and more than a few people on the internet freaked out. Fortunately, this great guy named Nathan came to the rescue 🙃.
.xipfile is just a
.zipwith a signature to verify that the file has not changed since its creator saved it. This protects from both damage from a disk error and from a third-party tampering with the file.