Add some magenta versionning information

README.md

@@ -41,6 +41,12 @@ In Hands-On Music Generation with Magenta, we explore the role of deep learning
 
 ## Magenta Versioning
 
+In the book, we use Magenta 1.1.7, but we provide updated code here, up to Magenta 2.1.2. The `master` branch corresponds to Magenta 1.1.7, and the `magenta-master` branch corresponds to Magenta 2.1.2 (for now). On the `magenta-master` branch, you can check the modifications (on the first example, for example) to migrate from 1.1.7 to 2.1.2 using:
+
+```bash
+git diff master Chapter02/chapter_02_example_01.py`
+```
+
 You can see what Magenta version you should be using by looking at the badge at the top of the README and in the Python files.
 
 - [**Magenta v1.1.7** (in the `master` branch)](https://github.com/PacktPublishing/hands-on-music-generation-with-magenta) - The book's code uses Magenta 1.1.7 which, at the time of publication, was the latest stable available version. The code for that version is in the default `master` branch and will stay there.