container, service: Support reloading containers on template file change

roles/container/defaults/main.yaml

@@ -14,3 +14,4 @@ container_auto_update: true
 container_requires: []
 container_wants: []
 container_add_capabilities: []
+container_reload_method: none

roles/container/handlers/main.yaml

@@ -4,3 +4,9 @@
     systemd_restart_units: "{{ systemd_restart_units + [container_name ~ '.service'] }}" # noqa: var-naming[no-role-prefix]
   changed_when: true
   notify: Apply systemd unit restarts
+
+- name: Reload container service {{ container_name }}
+  ansible.builtin.systemd_service:
+    name: "{{ container_name }}.service"
+    state: reloaded
+  when: "container_name ~ '.service' not in systemd_restart_units"

roles/container/meta/argument_specs.yaml

@@ -212,3 +212,21 @@ argument_specs:
         type: bool
         required: false
         default: true
+      container_reload_method:
+        description: |
+          How to reload configuration when systemctl reload is called
+          kill: Sends SIGHUP to the container
+          command: Runs the specified command inside the container
+        type: str
+        required: false
+        default: none
+        choices:
+          - kill
+          - command
+          - none
+      container_reload_command:
+        description: >-
+          Command to run inside container when systemctl reload is called.
+          Required if container_reload_method is command, ignored otherwise.
+        type: str
+        required: false

roles/container/vars/main/general.yaml

@@ -69,6 +69,10 @@ _container_labels: >-
     else {}
   }}
 
+_container_reload_commands:
+  kill: podman kill --signal HUP {{ container_name }}
+  command: podman exec {{ container_name }} {{ container_reload_command }}
+
 _container_quadlet_unit_options: |
   [Unit]
   Description=Container {{ container_name }}
@@ -90,8 +94,12 @@ _container_quadlet_auto_start_options: |
 
   [Install]
   WantedBy=multi-user.target
+_container_quadlet_reload_options: |
+  [Service]
+  ExecReload={{ _container_reload_commands[container_reload_method] }}
 _container_quadlet_options_incl_empty:
   - "{{ 'AutoUpdate=registry' if container_auto_update else '' }}"
   - "{{ _container_quadlet_unit_options }}"
   - "{{ _container_quadlet_auto_start_options if container_auto_start else '' }}"
+  - "{{ _container_quadlet_reload_options if container_reload_method != 'none' else '' }}"
 _container_quadlet_options: "{{ _container_quadlet_options_incl_empty | select('!=', '') }}"