$ git clone -n https://src.fedoraproject.org/rpms/R-blob.git /var/lib/mock/f45-build-5991-345/root/chroot_tmpdir/scmroot/R-blob
Cloning into '/var/lib/mock/f45-build-5991-345/root/chroot_tmpdir/scmroot/R-blob'...
$ git fetch origin 8c7b2d2c0348e1a904678c6a8984a405b96b8f76:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-blob
 * [new ref]         8c7b2d2c0348e1a904678c6a8984a405b96b8f76 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8c7b2d2 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild