$ git clone -n https://src.fedoraproject.org/rpms/rubygem-mini_mime.git /var/lib/mock/f45-build-35093-693/root/chroot_tmpdir/scmroot/rubygem-mini_mime
Cloning into '/var/lib/mock/f45-build-35093-693/root/chroot_tmpdir/scmroot/rubygem-mini_mime'...
$ git fetch origin 21e3d02e4f6230bb3662a5047a0816e98d0c707e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-mini_mime
 * [new ref]         21e3d02e4f6230bb3662a5047a0816e98d0c707e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 21e3d02 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild