The Git Mental Model
This is the section that makes the rest of the course easy. Instead of memorizing commands, you build a picture: four areas that a change travels through, commits as snapshots chained together, branches as movable labels, and a handful of names Git uses for "here", "there" and "the newest". Every command in Sections 5 to 12 will be described as a movement inside this picture. It ends with an interactive simulator where you can try the movements without touching a real repository.
Before you start: Section 1, at least lessons 1.1, 1.7 and 1.10. No installation is needed for this section.