Add debug helper script

I'm not sure if others will find this useful, but I use this
script to run pieces of devstack while trying to write/debug
things. It saves me a lot of time being able to get to some
project-lib function without a full clean/re-stack.

Figured I'd share in case it's worth putting into the tree.

Change-Id: I9a92fa71d34f50c2f5ba7d11c1a45301bd4478bf

tools/debug_function.sh

@@ -0,0 +1,24 @@
+#!/bin/bash
+
+# This is a small helper to speed development and debug with devstack.
+# It is intended to help you run a single function in a project module
+# without having to re-stack.
+#
+# For example, to run the just start_glance function, do this:
+#
+#   ./tools/debug_function.sh glance start_glance
+
+if [ ! -f "lib/$1" ]; then
+    echo "Usage: $0 [project] [function] [function...]"
+fi
+
+source stackrc
+source lib/$1
+shift
+set -x
+while [ "$1" ]; do
+    echo ==== Running $1 ====
+    $1
+    echo ==== Done with $1 ====
+    shift
+done