$ git clone -n https://src.fedoraproject.org/forks/u2fsdgvkx1/rpms/gcc.git /var/lib/mock/f45-bootstrap-219-130/root/chroot_tmpdir/scmroot/gcc
Cloning into '/var/lib/mock/f45-bootstrap-219-130/root/chroot_tmpdir/scmroot/gcc'...
$ git fetch origin 8a0ffad77f958158f0e015b51aac0ae211c44db2:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/forks/u2fsdgvkx1/rpms/gcc
 * [new ref]         8a0ffad77f958158f0e015b51aac0ae211c44db2 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8a0ffad add RVA23 support