Zuul roles: allow to build only a specific image

Useful to generate a single image on-the-fly
and use it for scenario tests
(or simply useful for a refactor of the rest of the
build-images script).

Change-Id: Ica615e9e7d93b38fd12189a9f97d26ca62d84a3e

roles/build-sahara-images-dib/defaults/main.yaml

@@ -2,3 +2,5 @@
 sahara_image_elements_src_dir: "{{ zuul.projects['git.openstack.org/openstack/sahara-image-elements'].src_dir }}"
 sahara_build_directory: /var/tmp/sahara-image-build
 sahara_plugin: vanilla
+sahara_plugin_version: ''
+sahara_plugin_distro: ''

roles/build-sahara-images-dib/tasks/main.yaml

@@ -1,4 +1,4 @@
 - name: Build all the images for the selected plugin
-  command: ./tools/gate/build-images "{{ sahara_plugin }}"
+  command: ./tools/gate/build-images "{{ sahara_plugin }}" "{{ sahara_plugin_version }}" "{{ sahara_plugin_distro }}"
   args:
     chdir: "{{ sahara_image_elements_src_dir }}"

tools/gate/build-images

@@ -1,7 +1,35 @@
 #!/bin/bash -xe
 
 PLUGIN=$1
+PLUGIN_VERSION=${2:-''}
+PLUGIN_DISTRO=${3:-''}
+
 export DIB_MIN_TMPFS=10
+
+# build a specific version if requested
+if [ -n "${PLUGIN}" ] && [ -n "${PLUGIN_VERSION}" ] && [ -n "${PLUGIN_DISTRO}" ]; then
+    case ${PLUGIN} in
+        vanilla|cloudera|ambari)
+            VERSION_FLAG="-v ${PLUGIN_VERSION}"
+            ;;
+        mapr)
+            VERSION_FLAG="-r ${PLUGIN_VERSION}"
+            ;;
+        spark)
+            VERSION_FLAG="-s ${PLUGIN_VERSION}"
+            ;;
+        storm)
+            VERSION_FLAG="-t ${PLUGIN_VERSION}"
+            ;;
+        *)
+            VERSION_FLAG=""
+            ;;
+    esac
+    tox -e venv -- sahara-image-create -x -u -p ${PLUGIN} -i ${PLUGIN_DISTRO} ${VERSION_FLAG}
+    exit
+fi
+
+# build (almost) all versions for a specified plugin
 case "$PLUGIN" in
     "vanilla")
         # temporary don't test building fedora image