Make image archive/save idempotent, using image id and repo tags as keys (#500)

tests/unit/plugins/test_support/docker_image_archive_stubbing.py

@@ -0,0 +1,76 @@
+# Copyright 2022 Red Hat | Ansible
+# 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
+
+from __future__ import (absolute_import, division, print_function)
+__metaclass__ = type
+
+import json
+import tarfile
+from tempfile import TemporaryFile
+
+
+def write_imitation_archive(file_name, image_id, repo_tags):
+    '''
+    Write a tar file meeting these requirements:
+
+    * Has a file manifest.json
+    * manifest.json contains a one-element array
+    * The element has a Config property with "[image_id].json" as the value name
+
+    :param file_name: Name of file to create
+    :type file_name: str
+    :param image_id: Fake sha256 hash (without the sha256: prefix)
+    :type image_id: str
+    :param repo_tags: list of fake image:tag's
+    :type repo_tags: list
+    '''
+
+    manifest = [
+        {
+            'Config': '%s.json' % image_id,
+            'RepoTags': repo_tags
+        }
+    ]
+
+    write_imitation_archive_with_manifest(file_name, manifest)
+
+
+def write_imitation_archive_with_manifest(file_name, manifest):
+    tf = tarfile.open(file_name, 'w')
+    try:
+        with TemporaryFile() as f:
+            f.write(json.dumps(manifest).encode('utf-8'))
+
+            ti = tarfile.TarInfo('manifest.json')
+            ti.size = f.tell()
+
+            f.seek(0)
+            tf.addfile(ti, f)
+
+    finally:
+        # In Python 2.6, this does not have __exit__
+        tf.close()
+
+
+def write_irrelevant_tar(file_name):
+    '''
+    Create a tar file that does not match the spec for "docker image save" / "docker image load" commands.
+
+    :param file_name: Name of tar file to create
+    :type file_name: str
+    '''
+
+    tf = tarfile.open(file_name, 'w')
+    try:
+        with TemporaryFile() as f:
+            f.write('Hello, world.'.encode('utf-8'))
+
+            ti = tarfile.TarInfo('hi.txt')
+            ti.size = f.tell()
+
+            f.seek(0)
+            tf.addfile(ti, f)
+
+    finally:
+        tf.close()