Keeping private fork requires non-trivial design skills. In the ideal case, you'd add hooks as part of public improvements (item 2), and use only those hooks in

Keeping private fork requires non-trivial design skills. In the ideal case, you'd add hooks as part of public improvements (item 2), and use only those hooks in your private changes. If you add appropriate tests to public project, this will increase the chances of your hooks staying unbroken.