$ git clone -n https://src.fedoraproject.org/rpms/R-stringr.git /var/lib/mock/f45-build-6447-348/root/chroot_tmpdir/scmroot/R-stringr
Cloning into '/var/lib/mock/f45-build-6447-348/root/chroot_tmpdir/scmroot/R-stringr'...
$ git fetch origin 5184dfb78ce0eeccca7177dd52d3c6170d4db05d:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-stringr
 * [new ref]         5184dfb78ce0eeccca7177dd52d3c6170d4db05d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 5184dfb Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild