propagate the headless state to all children

src/packme/PackerTemplate.py

@@ -190,6 +190,7 @@ class PackerTemplate:
                 parent_builder["iso_url"] = os.path.join(builder["output_directory"],"{}-{}".format(parent_template.name, builder_name))
                 parent_builder["iso_checksum_type"] = "none"
                 parent_builder["iso_checksum_url"] = "none"
+                parent_builder["headless"] = "{{ headless }}"
                 self._builders.insert(0,parent_builder)
 
             # If the builder is also defined in the child config, use the child config one and specify the image dependency
@@ -202,6 +203,7 @@ class PackerTemplate:
                 builder["iso_url"] = os.path.join(self._templates_base_dir,parent_template.name,"builds","{}-{}".format(parent_template.name, builder_name))
                 builder["iso_checksum_type"] = "none"
                 builder["iso_checksum_url"] = "none"
+                builder["headless"] = "{{ headless }}"
 
     def _load_packages(self, packages: List[str]):
         """Load the non-standard package YAML file and append them as provisioners of this :class:`PackerTemplate`.