$ git clone -n https://src.fedoraproject.org/forks/u2fsdgvkx1/rpms/gcc.git /var/lib/mock/f45-build-354-196/root/chroot_tmpdir/scmroot/gcc
Cloning into '/var/lib/mock/f45-build-354-196/root/chroot_tmpdir/scmroot/gcc'...
$ git fetch origin 8c86ceb58e1e16237a134c50d69a932f4661e2c9:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/forks/u2fsdgvkx1/rpms/gcc
 * [new ref]         8c86ceb58e1e16237a134c50d69a932f4661e2c9 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8c86ceb add RVA23 support