Hello, I was maintaining subsurface in Debian for a while.
In subsurface, they keep forking libraries. In Debian, it's not allowed to have source packages containing forked libraries. This is due to the fact that the security team doesn't want to have to find multiple copies of the same bug in libraries which might have slight differencies, and apply fixes in all of the copies. In my opinion it's a very sensible approach. I don't know what the policies in other distributions are, about duplicated source code. Unfortunately in subsurface, they don't care about any of this, and keep forking libraries. While libdivecomputer isn't problematic, because it is the only project using it, libmarble and libgit2 pose a problem, and they are internet facing, so could have security vulnerabilities. Upstream is not willing to help in using the original libraries rather than the forks, so a huge amount of patches is necessary to keep this package in Debian. The alternative is to delete all parts of code that use those libraries, and lose many functionalities. I am not closing this bug, but if anyone is reading this, my advice is to move on and don't try to package it. Best
