$ git clone -n https://src.fedoraproject.org/rpms/why3.git /var/lib/mock/f40-build-2440898-60987/root/chroot_tmpdir/scmroot/why3
Cloning into '/var/lib/mock/f40-build-2440898-60987/root/chroot_tmpdir/scmroot/why3'...
$ git fetch origin 84cb61b8ea83632f544fbefc84545ec0c79557d1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/why3
 * [new ref]         84cb61b8ea83632f544fbefc84545ec0c79557d1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 84cb61b Build again because koji ran out of disk space