Add a test for --shuffle option.

t/140-shuffle/all.do

@@ -0,0 +1,19 @@
+exec >&2
+. ../skip-if-minimal-do.sh
+
+# Need to repeat this several times, on the off chance that shuffling the
+# input happens to give us the same output (probability 1/factorial(9))
+x=0
+while [ "$x" -lt 10 ]; do
+    x=$(($x + 1))
+    rm -f out.log
+    redo --shuffle 1.x 2.x 3.x 4.x 5.x 6.x 7.x 8.x 9.x
+    sort out.log >sort.log
+    if ! diff -q out.log sort.log >/dev/null; then
+        exit 0
+    fi
+    echo "retry: #$x"
+done
+
+# still not shuffled?
+exit 22