I've made the library as part of my work on demoit.app where I need to store multiple files and their different versions. Storing all the content every time simply doesn't scale so I needed a smarter approach. Something like Git but running in the browser. It needed to be lightweight and to provide similar diff/patch experience. That's what Gitfred is.
The Function-as-child component or the so called FaCC is one of the most popular patterns in React nowadays. There are numerous libraries using this approach and this article is revealing how it works.