make packer inventory groups clearer and allow defining no extra

Author: sjpb

.github/workflows/doca.yml

@@ -92,7 +92,7 @@ jobs:
           -var-file=$PKR_VAR_environment_root/${{ env.CI_CLOUD }}.pkrvars.hcl \
           -var "source_image_name=${{ matrix.build.source_image_name }}" \
           -var "image_name=openhpc-doca" \
-          -var "groups=doca" \
+          -var "inventory_groups=doca" \
           openstack.pkr.hcl
         
       - name: Get created image names from manifest

packer/openstack.pkr.hcl

@@ -132,11 +132,11 @@ variable "metadata" {
   default = {}
 }
 
-variable "groups" {
+variable "inventory_groups" {
   type = string
-  description = "Comma-separated list of additional inventory groups (other than 'builder') to add build VM to"
-  default = "" # this is 
-  # rocky-latest = ["update"]
+  description = "Comma-separated list of additional inventory groups (other than 'builder') to add build VM to. Default is none."
+  default = ""
+  # rocky-latest = ["update"] # TODO: fix this in workflow
   # openhpc = ["control", "compute", "login"]
 }
 
@@ -206,7 +206,7 @@ build {
 
   provisioner "ansible" {
     playbook_file = "${var.repo_root}/ansible/fatimage.yml"
-    groups = concat(["builder"], split(",", var.groups))
+    groups = concat(["builder"], var.inventory_groups == "" ? [] : split(",", var.inventory_groups))
     keep_inventory_file = true # for debugging
     use_proxy = false # see https://www.packer.io/docs/provisioners/ansible#troubleshooting
     extra_arguments = [