add an image_list tool

this is an interface from devstack to provide a more robust
listing of the possible image urls that we might ask for during
a devstack run. This allows tools like nodepool, or 3rd party CI
systems to precache all this content in advance.

Change-Id: I7474f553ecf28e51a2340bef5bcefa962dbadc24

tools/image_list.sh

@@ -0,0 +1,35 @@
+#!/bin/bash
+
+# Keep track of the devstack directory
+TOP_DIR=$(cd $(dirname "$0")/.. && pwd)
+
+source $TOP_DIR/functions
+
+# Possible virt drivers, if we have more, add them here. Always keep
+# dummy in the end position to trigger the fall through case.
+DRIVERS="openvz ironic libvirt vsphere xenserver dummy"
+
+# Extra variables to trigger getting additional images.
+ENABLED_SERVICES=h-api
+HEAT_FETCHED_TEST_IMAGE="Fedora-i386-20-20131211.1-sda"
+
+# Loop over all the virt drivers and collect all the possible images
+ALL_IMAGES=""
+for driver in $DRIVERS; do
+    VIRT_DRIVER=$driver
+    URLS=$(source $TOP_DIR/stackrc && echo $IMAGE_URLS)
+    if [[ ! -z "$ALL_IMAGES" ]]; then
+        ALL_IMAGES+=,
+    fi
+    ALL_IMAGES+=$URLS
+done
+
+# Make a nice list
+echo $ALL_IMAGES | tr ',' '\n' | sort | uniq
+
+# Sanity check - ensure we have a minimum number of images
+num=$(echo $ALL_IMAGES | tr ',' '\n' | sort | uniq | wc -l)
+if [[ "$num" -lt 5 ]]; then
+    echo "ERROR: We only found $num images in $ALL_IMAGES, which can't be right."
+    exit 1
+fi