yes it is, but still you need to go though all detailed changes, it is not the case fortunately for the other parts of phoenix.
Core_components, given it is very probably changed by the user is not very upgrade friendly at the moment
Every generated content is really easy to upgrade.
Firstly you need 2 temporary directories let’s call them old and new. In both directories you need to call the same generator with exactly same parameters. The only difference is that the project in old directory would be generated with a older version of specific generator and project in new directory would be generated with a newer version of said generator.
Secondly you need to compare those directories by software of your choice for example by creating a .patch file and finally apply changes back to your original project. All you have to do is to fix the conflicts most likely always choosing the old version which would be your custom code.
Sometimes depending on generated content you would need to update your custom code as well, because for example it can contain a deprecated function calls which isn’t anything new when you update your dependency anyway.