Advice on structuring a Git repo into branches for an iterative tutorial

I'm a teacher and I'm about to publish a tutorial on how a build a PHP app in several iterative steps. At each iteration, I want to provide access to the associated source code and differences with the code of the previous iteration.

Naturally, I plan on using a Git repository for the project source code with a branch for each iteration. However, I wonder about future fixes and updates to my different branches. If I make a fix on a branch (say, iteration-03), I'd like it to "propagate" to all upcoming branches (iteration-04, iteration-05, and so on). My branches diffs must also stay coherent.

So my questions are :

• What is be the best way to structure a Git repo into branches to achieve my goal ?


• How to propagate fixes to a branch into the following ones ?

Thanks in advance for your answers.

Regards, Baptiste