$ git clone -n https://src.fedoraproject.org/rpms/R-systemfonts.git /var/lib/mock/f40-build-1930456-25111/root/chroot_tmpdir/scmroot/R-systemfonts
Cloning into '/var/lib/mock/f40-build-1930456-25111/root/chroot_tmpdir/scmroot/R-systemfonts'...
$ git fetch origin e26328a4dab4d112b404eb9682866fb7367350f9:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-systemfonts
 * [new ref]         e26328a4dab4d112b404eb9682866fb7367350f9 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e26328a R-maint-sig mass rebuild