GitHub: link to files in GitHub Project

I create a tutorial, where I want to introduce some testing frameworks like Mockito, WireMock and EasyMock. I want to explain it step by step. Additionaly I want to provide examples, where the reader of the tutorial can try to recreate these. Therefore I want to to give them the opportunity to look into my source code and use it when they are not able to recreate the test. And then they can use the actual version to continue and then again, when they are not able to create the next test, I want to to give them the possibility to use my new version with the new test.

My idea is to use different commits and link them to the tutorial. How can I do this or is there any better approach to reach what I just explained?