$ git clone -n https://src.fedoraproject.org/rpms/R-rcmdcheck.git /var/lib/mock/f40-build-1824183-24918/root/chroot_tmpdir/scmroot/R-rcmdcheck
Cloning into '/var/lib/mock/f40-build-1824183-24918/root/chroot_tmpdir/scmroot/R-rcmdcheck'...
$ git fetch origin 42ed5b51433cae62a5fa66b483767ae691978dbf:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-rcmdcheck
 * [new ref]         42ed5b51433cae62a5fa66b483767ae691978dbf -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 42ed5b5 R-maint-sig mass rebuild