Apart from obvious reasons (keeping things clean, current, etc.), removing this copy makes it easier to deal with less-than-perfect build systems, such as Launchpad's "recipes" that can't pull in packaging information from an external repository when the target path already exists.
The debian/ subdirectory moved to https://github.com/Nitrokey/nitrokey-app.build
Apart from obvious reasons (keeping things clean, current, etc.), removing this copy makes it easier to deal with less-than-perfect build systems, such as Launchpad's "recipes" that can't pull in packaging information from an external repository when the target path already exists.