Fix docker_image's build.args (#456)

* Add tests for build.args.

* Fix bug: store build args in correct dict

* Add changelog fragment.

* Update copyright notice.

tests/integration/targets/docker_image/tasks/test.yml

@@ -24,6 +24,7 @@
     src: '{{ item }}'
     dest: '{{ remote_tmp_dir }}/files/{{ item }}'
   loop:
+    - ArgsDockerfile
     - Dockerfile
     - EtcHostsDockerfile
     - MyDockerfile

tests/integration/targets/docker_image/tasks/tests/options.yml

@@ -27,7 +27,9 @@
     name: "{{ iname }}"
     build:
       path: "{{ remote_tmp_dir }}/files"
+      dockerfile: "ArgsDockerfile"
       args:
+        IMAGE: "{{ docker_test_image_busybox }}"
         TEST1: val1
         TEST2: val2
         TEST3: "True"
@@ -41,7 +43,9 @@
     name: "{{ iname }}"
     build:
       path: "{{ remote_tmp_dir }}/files"
+      dockerfile: "ArgsDockerfile"
       args:
+        IMAGE: "{{ docker_test_image_busybox }}"
         TEST1: val1
         TEST2: val2
         TEST3: "True"

tests/integration/targets/docker_image/templates/ArgsDockerfile

@@ -0,0 +1,13 @@
+# Copyright (c) 2022, Felix Fontein
+# GNU General Public License v3.0+ (see LICENSES/GPL-3.0-or-later.txt or https://www.gnu.org/licenses/gpl-3.0.txt)
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+ARG IMAGE
+ARG TEST1
+ARG TEST2
+ARG TEST3
+
+FROM ${IMAGE}
+ENV foo /bar
+WORKDIR ${foo}
+RUN echo "${TEST1} - ${TEST2} - ${TEST3}"