$ git clone -n https://src.fedoraproject.org/rpms/R-gert.git /var/lib/mock/f45-build-6127-346/root/chroot_tmpdir/scmroot/R-gert
Cloning into '/var/lib/mock/f45-build-6127-346/root/chroot_tmpdir/scmroot/R-gert'...
$ git fetch origin 41a858cb1d44cd735af5de574583f37e19c2b10d:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-gert
 * [new ref]         41a858cb1d44cd735af5de574583f37e19c2b10d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 41a858c Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild