$ git clone -n https://src.fedoraproject.org/rpms/rubygem-builder.git /var/lib/mock/f39-build-1458089-33035/root/chroot_tmpdir/scmroot/rubygem-builder
Cloning into '/var/lib/mock/f39-build-1458089-33035/root/chroot_tmpdir/scmroot/rubygem-builder'...
$ git fetch origin 0ad84a499378595bad064f7f9284bfdea67c1ab9:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-builder
 * [new ref]         0ad84a499378595bad064f7f9284bfdea67c1ab9 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 0ad84a4 Rebuilt for https://fedoraproject.org/wiki/Fedora_39_Mass_Rebuild