$ git clone -n https://src.fedoraproject.org/rpms/R-nanotime.git /var/lib/mock/f41-build-side-1-2749592-31004/root/chroot_tmpdir/scmroot/R-nanotime
Cloning into '/var/lib/mock/f41-build-side-1-2749592-31004/root/chroot_tmpdir/scmroot/R-nanotime'...
$ git fetch origin 0b68d783270441b77a97b260bddc84627bdf461b:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-nanotime
 * [new ref]         0b68d783270441b77a97b260bddc84627bdf461b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 0b68d78 convert GPLv2+ license to SPDX