$ git clone -n https://src.fedoraproject.org/rpms/rubygem-rackup.git /var/lib/mock/f45-build-35211-694/root/chroot_tmpdir/scmroot/rubygem-rackup
Cloning into '/var/lib/mock/f45-build-35211-694/root/chroot_tmpdir/scmroot/rubygem-rackup'...
$ git fetch origin 952e973b2ad8003f9744c4be3b0caf2d3079c19e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-rackup
 * [new ref]         952e973b2ad8003f9744c4be3b0caf2d3079c19e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 952e973 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild