test: provider usage text for shell test runner

test/test-shell.sh

@@ -1,6 +1,12 @@
 #!/bin/bash
 # simple test harness for testing mgmt
 # NOTE: this will rm -rf /tmp/mgmt/
+if [ "$1" == "--help" ] || [ "$1" == "-h" ]; then
+	echo -e "usage: ./"`basename $0`" [[--help] | <test>]"
+	echo -e "where: <test> is empty to run all tests, or <file>.sh from shell/ dir"
+	exit 1
+fi
+
 echo running test-shell.sh
 set -o errexit
 set -o pipefail