$ git clone -n https://src.fedoraproject.org/rpms/R-cli.git /var/lib/mock/f38-build-724271-99404/root/chroot_tmpdir/scmroot/R-cli
Cloning into '/var/lib/mock/f38-build-724271-99404/root/chroot_tmpdir/scmroot/R-cli'...
$ git fetch origin b979df7bffd9b8bbe4a71356693c77e891e02c11:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-cli
 * [new ref]         b979df7bffd9b8bbe4a71356693c77e891e02c11 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b979df7 R-maint-sig mass rebuild