How to link the code of two almost identical Android apps?

Question

Android

There are two apps - free with ads and paid without ads. That is, the difference between them is minimal. How to organize their relationship at the level of storing files and making changes so as not to engage in copy-paste? After all, these are two different projects, two different directories, two different gits... If only the code was common, then it would be possible to move it to the library. But everything is the same here, including resources (which, nevertheless, can also change).

Answer 1

in the part that is responsible for "show / not show" the code, check which version of the program is installed and, depending on this, either show or not, then a second copy of the program is not required.

Answer 2

I didn’t understand why there are two builds when all the difference can be fit in one condition? Use build flavor. https://developer.android.com/tools/building/config...