I thought your question was more or less: “How do I build n8n locally for testing/modifying with docker?”
And my answer is that you do not need Docker to build n8n as n8n is a regular Node.js application. There is no need for Docker at all. Sure you can run it in Docker if you want (like I do) but you can also just run it directly on your computer without Docker as most people do.
If you want to modify n8n and release your own Docker image you would either have to publish all of the n8n npm modules you made changes to, to npm and then reference these new modules in your package.json file. Or you would have to link everything with lerna like in the
CONTRIBUTING.md file described (probably easier) and then publish that.
The second example I gave you is an example Dockerfile which runs Node.js and in which you can run n8n. It is meant for development. Again you would have to then mount the n8n-folder and follow the CONTRIBUTING.md guide.
Never heard about real and unreal Dockerfiles. But if only one that links and builds all the modules and is then deployable like that is real, then there is currently sadly only the unreal one. You are however very welcome to create also the “real” one and open a pull-request. I am sure some people would find it useful.
About how other contributors do it. They either have Node.js installed locally or they use a Dockerfile similar to the one I did post and follow what is written in the