hush: Print error messages on shift -1

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/shell/hush_test/hush-misc/shift1.tests b/shell/hush_test/hush-misc/shift1.tests
new file mode 100755
index 0000000..f2a2647
--- /dev/null
+++ b/shell/hush_test/hush-misc/shift1.tests
@@ -0,0 +1,10 @@
+$THIS_SH -c 'shift;    echo "$@"' 0 1 2 3 4
+#We complain on -1 and continue.
+$THIS_SH -c 'shift -1; echo "$@"' 0 1 2 3 4
+$THIS_SH -c 'shift  0; echo "$@"' 0 1 2 3 4
+$THIS_SH -c 'shift  1; echo "$@"' 0 1 2 3 4
+$THIS_SH -c 'shift  2; echo "$@"' 0 1 2 3 4
+$THIS_SH -c 'shift  3; echo "$@"' 0 1 2 3 4
+$THIS_SH -c 'shift  4; echo "$@"' 0 1 2 3 4
+$THIS_SH -c 'shift  5; echo "$@"' 0 1 2 3 4
+$THIS_SH -c 'shift  6; echo "$@"' 0 1 2 3 4