$ git clone -n https://src.fedoraproject.org/rpms/R.git /var/lib/mock/f38-build-side-42-init-devel-664416-26644/root/chroot_tmpdir/scmroot/R
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-664416-26644/root/chroot_tmpdir/scmroot/R'...
$ git fetch origin 01100a409ad4bc697726ac68e2e63ba50f743020:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R
 * [new ref]         01100a409ad4bc697726ac68e2e63ba50f743020 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 01100a4 Update to 4.2.3