Fix idempotency for tagging local images (#980)

Signed-off-by: Jeoffrey Bakker <jeoffreybakker@users.noreply.github.com>

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

@@ -13,6 +13,22 @@
         target_names:
           - openjdk8
           - jdk8
+      register: tag_result
+
+    - name: Tag image again to test idempotency
+      containers.podman.podman_tag:
+        executable: "{{ test_executable | default('podman') }}"
+        image: docker.io/library/alpine
+        target_names:
+          - openjdk8
+          - jdk8
+      register: tag_result_idempotency
+
+    - name: Check idempotency
+      assert:
+        that:
+          - tag_result.changed == true
+          - tag_result_idempotency.changed == false
 
     - name: Get tagged image info
       containers.podman.podman_image_info:

tests/unit/plugins/modules/test_podman_tag.py

@@ -0,0 +1,22 @@
+from __future__ import absolute_import, division, print_function
+
+__metaclass__ = type
+
+import pytest
+
+from ansible_collections.containers.podman.plugins.modules.podman_tag import create_full_qualified_image_name
+
+
+@pytest.mark.parametrize(
+    "test_input, expected",
+    [
+        ("alpine", "localhost/alpine:latest"),
+        ("alpine:3.19", "localhost/alpine:3.19"),
+        ("docker.io/library/alpine", "docker.io/library/alpine:latest"),
+        ("docker.io/alpine", "docker.io/library/alpine:latest"),
+        ("docker.io/alpine@sha256:1234567890abcdef", "docker.io/library/alpine@sha256:1234567890abcdef"),
+    ],
+)
+def test_create_full_qualified_image_name(test_input, expected):
+    print(create_full_qualified_image_name.__code__.co_filename)
+    assert create_full_qualified_image_name(test_input) == expected