$ git clone -n https://src.fedoraproject.org/rpms/R-foghorn.git /var/lib/mock/f40-build-1944409-25177/root/chroot_tmpdir/scmroot/R-foghorn
Cloning into '/var/lib/mock/f40-build-1944409-25177/root/chroot_tmpdir/scmroot/R-foghorn'...
$ git fetch origin 21161c35d484df90a9fb8a14542e2283c7abf6b9:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-foghorn
 * [new ref]         21161c35d484df90a9fb8a14542e2283c7abf6b9 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 21161c3 R-maint-sig mass rebuild