$ git clone -n https://src.fedoraproject.org/rpms/R-tibble.git /var/lib/mock/f45-build-6455-348/root/chroot_tmpdir/scmroot/R-tibble
Cloning into '/var/lib/mock/f45-build-6455-348/root/chroot_tmpdir/scmroot/R-tibble'...
$ git fetch origin 2d62921b46bfd278316f13a0a3b88e5cc42b48f9:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-tibble
 * [new ref]         2d62921b46bfd278316f13a0a3b88e5cc42b48f9 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 2d62921 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild