$ git clone -n https://src.fedoraproject.org/rpms/golang-x-arch.git /var/lib/mock/f38-build-side-42-init-devel-685186-26759/root/chroot_tmpdir/scmroot/golang-x-arch
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-685186-26759/root/chroot_tmpdir/scmroot/golang-x-arch'...
$ git fetch origin 21d4a43a07a686457651501f8830e9abdb4e71e8:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/golang-x-arch
 * [new ref]         21d4a43a07a686457651501f8830e9abdb4e71e8 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 21d4a43 Update to latest version (#2173338)