How to update an open source CMS with GitHub?

Question

CMS

There is a site created on an open source CMS, in which I regularly make changes to fit my needs.
How to update the CMS with GitHub when a new version is released so as not to lose your changes in the code?

Answer 1

As I understand it, above you were advised not to pick the core of the CMS yourself, then it is easier to perform updates.
With the right approach, this is done like this: there is the CMS itself, which is regularly updated, and there are extensions that are written for a specific site, and which are updated by the site developer. And these two spheres, in general, should not intersect. Then updating the CMS itself will in no way affect your code. Although, of course, sometimes you have to change the extension code if the API for working with the kernel changes, or the structure of the database, etc.
If it doesn’t work out without intervention in the CMS core, then there is only one option - to fork this CMS, and when a new version of it is released, carefully merge the changes with your hands, and then upload them to the site

Answer 2

Store in the repository only the files you change, then just copy the new version of the CMS and see if something has changed in the files you change.
And in a good way, try not to change the CMS core, but work through the built-in API