$ git clone -n https://src.fedoraproject.org/rpms/R-bench.git /var/lib/mock/f42-build-3530679-46321/root/chroot_tmpdir/scmroot/R-bench
Cloning into '/var/lib/mock/f42-build-3530679-46321/root/chroot_tmpdir/scmroot/R-bench'...
$ git fetch origin e12dda648b68803f5262ffddd1efe9bc41bca0a1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-bench
 * [new ref]         e12dda648b68803f5262ffddd1efe9bc41bca0a1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e12dda6 R-maint-sig mass rebuild