Barely anyone is going to go to the github, especially outside of HN, and only some of those people are going to read past the first image, so it's important that you get the most important information out there immediately. I glanced at the extended explanation and decided it would be faster to figure it out by putting stuff in the website. The instant visual feedback means you don't need to tell users every nuance of every command, but you do need to pick the specific details that users can use to learn everything else.