With the variety of Bronze, Silver and Gold challenges, and the need to keep them separate from the projects under construction through the chapters, I think it is a big missed opportunity not to devote some time in the book on Source Control.
I have been using Source Control to branch off the code to do the challenges, then load the original version to get back to the version without the challenge changes.
A proper tutorial on commit, check out, merging etc would be beneficial. I can’t seem to get check out to work, and I don’t know how to get it working. (User error or not set up correctly.)