$ git clone -n https://src.fedoraproject.org/rpms/R-jqr.git /var/lib/mock/f38-build-724217-99404/root/chroot_tmpdir/scmroot/R-jqr
Cloning into '/var/lib/mock/f38-build-724217-99404/root/chroot_tmpdir/scmroot/R-jqr'...
$ git fetch origin b6a9ddbf15f7475c9b743e34af7e3a11c2de2c84:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-jqr
 * [new ref]         b6a9ddbf15f7475c9b743e34af7e3a11c2de2c84 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b6a9ddb R-maint-sig mass rebuild