The first number of directory titles is just for sorting, the second number stands for the chapter. For example:
13-6.4-MathSin is found in
chapter 6.4 with file name
git clone firstname.lastname@example.org:appsunited/objective-c-nerd-ranch.git cd objective-c-nerd-ranch
Please feel free to copy and edit as you need! Comments, reviews and discussions are welcome!