$ git clone -n https://src.fedoraproject.org/rpms/gcc.git /var/lib/mock/f41-build-851712-166043/root/chroot_tmpdir/scmroot/gcc
Cloning into '/var/lib/mock/f41-build-851712-166043/root/chroot_tmpdir/scmroot/gcc'...
$ git fetch origin dc203d1b77666d6375f6e5e73dfa9d49a33392a3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gcc
 * [new ref]         dc203d1b77666d6375f6e5e73dfa9d49a33392a3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at dc203d1 14.2.1-3