Simplify playbook "role" to fall back to all hosts if not specified otherwise

role.yml

@@ -8,7 +8,7 @@
 - include: "validate.yml"
 
 - name: "Execute Role {{ role }}"
-  hosts: "{{ hosts }}"
+  hosts: "{{ hosts|default('all') }}"
   sudo: yes
   roles:
     - "{{ role }}"