You'll have to use something like https://github.com/dragotin/kraft/archive/%{git_full_sha}.tar.gz#/%{name}-%{version}.tar.gz or just %{name}-%{version}.tar.gz for Source0.

RPM essentially calls basename(Source...) on each provided URL to determine the dist name. The #/... trick is a very common hack in order to override the name if the last component in a URL doesn't directly match the desired name, since it's sent to the remote HTTP server as extra anchor data that doesn't change anything, but is also interpreted by RPM.

I originally put it in like this (including the empty %{git_full_sha} macro, which is not provided/defined anywhere and will also not be passed down via tar_scm or anything - it just doesn't exist but I've used it as a conceptional thing) as human documentation as to where to really get the sources. %{name}-%{version}.tar.gz would just equally work, since the tar_scm service generates the dist file and the actual Version: tag is overridden by the set_version service.