Add docker_image_export module (#774)

* Add docker_image_export module.

* Add basic tests.

* Add more seealsos.

tests/integration/targets/docker_image_export/tasks/main.yml

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+---
+# Copyright (c) Ansible Project
+# 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
+
+####################################################################
+# WARNING: These are designed specifically for Ansible tests       #
+# and should not be used as examples of how to write Ansible roles #
+####################################################################
+
+- when: ansible_facts.distribution ~ ansible_facts.distribution_major_version not in ['CentOS6', 'RedHat6']
+  include_tasks:
+    file: test.yml

tests/integration/targets/docker_image_export/tasks/run-test.yml

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+---
+# Copyright (c) Ansible Project
+# 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
+
+- name: "Loading tasks from {{ test_name }}"
+  include_tasks: "{{ test_name }}"

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

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+---
+# Copyright (c) Ansible Project
+# 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
+
+- name: Create random name prefix
+  set_fact:
+    name_prefix: "{{ 'ansible-docker-test-%0x' % ((2**32) | random) }}"
+- name: Create image and container list
+  set_fact:
+    inames: []
+    cnames: []
+
+- debug:
+    msg: "Using name prefix {{ name_prefix }}"
+
+- block:
+    - include_tasks: run-test.yml
+      with_fileglob:
+        - "tests/*.yml"
+      loop_control:
+        loop_var: test_name
+
+  always:
+    - name: "Make sure all images are removed"
+      docker_image_remove:
+        name: "{{ item }}"
+      with_items: "{{ inames }}"
+    - name: "Make sure all containers are removed"
+      docker_container:
+        name: "{{ item }}"
+        state: absent
+        force_kill: true
+      with_items: "{{ cnames }}"
+
+  when: docker_api_version is version('1.25', '>=')
+
+- fail: msg="Too old docker / docker-py version to run docker_image tests!"
+  when: not(docker_api_version is version('1.25', '>=')) and (ansible_distribution != 'CentOS' or ansible_distribution_major_version|int > 6)

tests/integration/targets/docker_image_export/tasks/tests/basic.yml

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+---
+# Copyright (c) Ansible Project
+# 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
+
+- set_fact:
+    image_names:
+      - "{{ docker_test_image_hello_world }}"
+      - "{{ docker_test_image_alpine_different }}"
+      - "{{ docker_test_image_alpine }}"
+
+- name: Make sure images are there
+  docker_image_pull:
+    name: "{{ item }}"
+  register: images
+  loop: "{{ image_names }}"
+
+- vars:
+    image_ids: "{{ images.results | map(attribute='image') | map(attribute='Id') | list }}"
+    all_images: "{{ image_names + (images.results | map(attribute='image') | map(attribute='Id') | list) }}"
+    image_tasks:
+      - file: archive-1.tar
+        images: "{{ image_names }}"
+      - file: archive-2.tar
+        images: "{{ image_ids }}"
+      - file: archive-3.tar
+        images:
+          - "{{ image_names[0] }}"
+          - "{{ image_ids[1] }}"
+      - file: archive-4.tar
+        images:
+          - "{{ image_ids[0] }}"
+          - "{{ image_names[0] }}"
+      - file: archive-5.tar
+        images:
+          - "{{ image_ids[0] }}"
+
+  block:
+    - name: Create archives
+      docker_image_export:
+        names: "{{ item.images }}"
+        path: "{{ remote_tmp_dir }}/{{ item.file }}"
+      loop: "{{ image_tasks }}"
+      loop_control:
+        label: "{{ item.file }}"
+      register: result
+
+    - name: Extract manifest.json files
+      command: tar xvf "{{ remote_tmp_dir }}/{{ item.file }}" manifest.json --to-stdout
+      loop: "{{ image_tasks }}"
+      loop_control:
+        label: "{{ item.file }}"
+      register: manifests
+
+    - name: Do basic tests
+      assert:
+        that:
+          - item.0.images | length == item.1 | length
+          - item.1 | unique | length == item.2 | length
+          - manifest_json_images == export_image_ids
+      loop: "{{ image_tasks | zip(export_images, manifests_json) }}"
+      loop_control:
+        label: "{{ item.0.file }}"
+      vars:
+        filenames: "{{ image_tasks | map(attribute='file') }}"
+        export_images: "{{ result.results | map(attribute='images') | map('map', attribute='Id') }}"
+        manifests_json: "{{ manifests.results | map(attribute='stdout') | map('from_json') }}"
+        manifest_json_images: "{{ item.2 | map(attribute='Config') | map('regex_replace', '.json$', '') | map('regex_replace', '^blobs/sha256/', '') | sort }}"
+        export_image_ids: "{{ item.1 | map('regex_replace', '^sha256:', '') | unique | sort }}"