In a number of cases I have seen 2 versions of ebuilds get generated – one with stable KEYWORDS and one with ~KEYWORDS (or alternatively empty KEYWORDS).
While github'py's release_gen allows us to include/exclude pre-releases , alex2101 it would be good for tag_gen to have a similar functionality, and I agree.
Use case: That way, e.g. systemd-tmpfiles-250 would be stable, and systemd-tmpfiles-251_rc1 would be keywords-masked