3.1 API conflicts
  3.1.1 Example 15
  3.1.2 Example 16
  3.1.3 Exercises
 3.2 Full file conflicts
  3.2.1 Example 17
  Stay on HEAD, bring over changes from the other branch
  3.2.2 Example 17 - again... with a twist
  3.2.3 Exercises
  3.2.4 Tips