Fix: Correctly report header copyright year changes

Previously, when a header was changed from e.g. `2025` to `2025-2026`,
this was reported as a change from `None` to `2026`. Similarly, a change
from `2024-2025` to `2024-2026` was reported as a change from `2025` to
`2026`.

Author: wiegandm

pontos/updateheader/updateheader.py

@@ -258,11 +258,19 @@ def update_file(
                     _substitute_license_text(
                         fp, line, copyright_regex, copyright_term
                     )
-                    print(
-                        f"{file}: Changed License Header Copyright Year "
-                        f"{copyright_match.modification_year} -> "
-                        f"{year}"
-                    )
+                    if with_multi_year:
+                        print(
+                            f"{file}: Changed License Header Copyright Year "
+                            f"{copyright_match.creation_year}-"
+                            f"{copyright_match.modification_year} -> "
+                            f"{copyright_match.creation_year}-{year}"
+                        )
+                    else:
+                        print(
+                            f"{file}: Changed License Header Copyright Year "
+                            f"{copyright_match.creation_year} -> "
+                            f"{copyright_match.creation_year}-{year}"
+                        )
                 else:
                     print(f"{file}: License Header is ok.")
 

tests/updateheader/test_header.py

@@ -327,7 +327,7 @@ def test_update_create_header_single_year(self, mock_stdout):
             )
 
     @patch("sys.stdout", new_callable=StringIO)
-    def test_update_header_in_file(self, mock_stdout):
+    def test_update_header_in_file_from_single_year(self, mock_stdout):
         year = "2021"
         license_id = "AGPL-3.0-or-later"
 
@@ -346,15 +346,42 @@ def test_update_header_in_file(self, mock_stdout):
             self.assertEqual(
                 ret,
                 f"{test_file}: Changed License Header "
-                "Copyright Year None -> 2021\n",
+                "Copyright Year 2020 -> 2020-2021\n",
             )
             self.assertIn(
                 "# SPDX-FileCopyrightText: 2020-2021 Greenbone AG",
                 test_file.read_text(encoding="utf-8"),
             )
 
     @patch("sys.stdout", new_callable=StringIO)
-    def test_update_header_in_file_single_year(self, mock_stdout):
+    def test_update_header_in_file_from_multi_year(self, mock_stdout):
+        year = "2021"
+        license_id = "AGPL-3.0-or-later"
+
+        header = HEADER.format(date="2018-2020")
+        with temp_file(
+            content=header, name="test.py", change_into=True
+        ) as test_file:
+            update_file(
+                test_file,
+                year,
+                license_id,
+                self.company,
+            )
+
+            ret = mock_stdout.getvalue()
+            self.assertEqual(
+                ret,
+                f"{test_file}: Changed License Header "
+                "Copyright Year 2018-2020 -> 2018-2021\n",
+            )
+            self.assertIn(
+                "# SPDX-FileCopyrightText: 2018-2021 Greenbone AG",
+                test_file.read_text(encoding="utf-8"),
+            )
+
+    @patch("sys.stdout", new_callable=StringIO)
+    def test_update_header_in_file_to_single_year(self, mock_stdout):
         year = "2021"
         license_id = "AGPL-3.0-or-later"