jdk-15-ga tag not in jdk15u

[Lindenmaier, Goetz]

Hi,

I would appreciate if you could pull the tag jdk-15-ga to 
jdk-updates/jdk15u.
Without that, it's not obvious whether all changes
that went into 15 are also in the 15u repo.
Also, you get two heads if you pull from both repos.

Thanks and best regards,
  Goetz.