Can you talk a bit more about what kind of code is being copied?
Most of that repository is a series of modules in their own directories (e.g., "src/modules/character").
The second repository is a Node.js API. The majority of its functionality comes from one of the modules from the first repository that I copy in its entirety to the other repository whenever I change it.
- Use git submodules. Have the node repo have a submodule on the app repo.
- Publish the shared code to a private registry (like github's package registry), and pull it in as an npm package.