bash completions: work correctly when $cur is an empty string.
bash completions: work correctly when $cur is an empty string.

Otherwise 'cd t/defaults-flat' then 'redo <tab>' doesn't show all the
possible targets.

rowhit/redo,pombredanne/redo,apenwarr/redo,dinkelk/redo-python,pombredanne/redo,apenwarr/redo,dinkelk/redo-python,dinkelk/redo-python,rowhit/redo,pombredanne/redo,apenwarr/redo,pombredanne/redo,rowhit/redo,apenwarr/redo,rowhit/redo,dinkelk/redo-python