I expect this to be the process forever going forward:
* Rawhide tracks glibc master.
* Fedora release is branched from Rawhide.
* glibc release is made upstream.
* Fedora branch is rebased on glibc upstream release
to include ABI guarantees.
* Fedora release goes GA.
The changes in the rebase should be minor since we've
been tracking master the whole time.