$ git clone -n https://src.fedoraproject.org/rpms/toolbox.git /var/lib/mock/f40-build-2608895-63749/root/chroot_tmpdir/scmroot/toolbox
Cloning into '/var/lib/mock/f40-build-2608895-63749/root/chroot_tmpdir/scmroot/toolbox'...
$ git fetch origin 6dfd366e611ea230785a598899e95d99cf2f5ebf:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/toolbox
 * [new ref]         6dfd366e611ea230785a598899e95d99cf2f5ebf -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6dfd366 Conditionalize the BuildRequires on golang