$ git clone -n https://src.fedoraproject.org/rpms/gnome-nibbles.git /var/lib/mock/f39-build-1577385-37962/root/chroot_tmpdir/scmroot/gnome-nibbles
Cloning into '/var/lib/mock/f39-build-1577385-37962/root/chroot_tmpdir/scmroot/gnome-nibbles'...
$ git fetch origin 3cb06149c9984fed8b35c59c8995fbd5965f8704:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gnome-nibbles
 * [new ref]         3cb06149c9984fed8b35c59c8995fbd5965f8704 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3cb0614 Update to 4.0.beta