$ git clone -n https://src.fedoraproject.org/rpms/R-utf8.git /var/lib/mock/f38-build-724189-99404/root/chroot_tmpdir/scmroot/R-utf8
Cloning into '/var/lib/mock/f38-build-724189-99404/root/chroot_tmpdir/scmroot/R-utf8'...
$ git fetch origin d4cb34f43cfa7fe40b9da59153a67f2f28f35b30:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-utf8
 * [new ref]         d4cb34f43cfa7fe40b9da59153a67f2f28f35b30 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at d4cb34f Ignore vignettes