Replace cloning repositories by fetching metadata through api.github.com

[MatousJobanek]

if it is possible to do it in this way

[bartoszmajsak]

It will make us even more dependent on the 3rd services - just a general thought. Maybe it would be good to investigate that as an alternative. There are few functionalities I believe where we do sth with the file contents (I guess that's for Maven dependencies for example).

I think we should investigate shallow cloning with only one, main branch to start with.