Refactor test fixtures to use shared create_args helper

Uses the real parse_args() function to get CLI defaults, so when
new arguments are added they're automatically available to all tests.

Changes:
- Add tests/conftest.py with create_args fixture
- Update 8 test files to use shared fixture
- Remove duplicate _create_mock_args methods
- Remove redundant @pytest.fixture mock_args definitions

This eliminates the need to update multiple test files when
adding new CLI arguments.

tests/test_skip_assets_on.py

@@ -1,7 +1,7 @@
 """Tests for --skip-assets-on flag behavior (issue #135)."""
 
 import pytest
-from unittest.mock import Mock, patch
+from unittest.mock import patch
 
 from github_backup import github_backup
 
@@ -13,52 +13,6 @@ class TestSkipAssetsOn:
     while still backing up release metadata.
     """
 
-    def _create_mock_args(self, **overrides):
-        """Create a mock args object with sensible defaults."""
-        args = Mock()
-        args.user = "testuser"
-        args.output_directory = "/tmp/backup"
-        args.include_repository = False
-        args.include_everything = False
-        args.include_gists = False
-        args.include_starred_gists = False
-        args.all_starred = False
-        args.skip_existing = False
-        args.bare_clone = False
-        args.lfs_clone = False
-        args.no_prune = False
-        args.include_wiki = False
-        args.include_issues = False
-        args.include_issue_comments = False
-        args.include_issue_events = False
-        args.include_pulls = False
-        args.include_pull_comments = False
-        args.include_pull_commits = False
-        args.include_pull_details = False
-        args.include_labels = False
-        args.include_hooks = False
-        args.include_milestones = False
-        args.include_releases = True
-        args.include_assets = True
-        args.skip_assets_on = []
-        args.include_attachments = False
-        args.incremental = False
-        args.incremental_by_files = False
-        args.github_host = None
-        args.prefer_ssh = False
-        args.token_classic = "test-token"
-        args.token_fine = None
-        args.as_app = False
-        args.osx_keychain_item_name = None
-        args.osx_keychain_item_account = None
-        args.skip_prerelease = False
-        args.number_of_latest_releases = None
-
-        for key, value in overrides.items():
-            setattr(args, key, value)
-
-        return args
-
     def _create_mock_repository(self, name="test-repo", owner="testuser"):
         """Create a mock repository object."""
         return {
@@ -123,10 +77,10 @@ class TestSkipAssetsOnBehavior(TestSkipAssetsOn):
     @patch("github_backup.github_backup.mkdir_p")
     @patch("github_backup.github_backup.json_dump_if_changed")
     def test_assets_downloaded_when_not_skipped(
-        self, mock_json_dump, mock_mkdir, mock_retrieve, mock_download
+        self, mock_json_dump, mock_mkdir, mock_retrieve, mock_download, create_args
     ):
         """Assets should be downloaded when repo is not in skip list."""
-        args = self._create_mock_args(skip_assets_on=[])
+        args = create_args(skip_assets_on=[])
         repository = self._create_mock_repository(name="normal-repo")
         release = self._create_mock_release()
         asset = self._create_mock_asset()
@@ -154,10 +108,10 @@ class TestSkipAssetsOnBehavior(TestSkipAssetsOn):
     @patch("github_backup.github_backup.mkdir_p")
     @patch("github_backup.github_backup.json_dump_if_changed")
     def test_assets_skipped_when_repo_name_matches(
-        self, mock_json_dump, mock_mkdir, mock_retrieve, mock_download
+        self, mock_json_dump, mock_mkdir, mock_retrieve, mock_download, create_args
     ):
         """Assets should be skipped when repo name is in skip list."""
-        args = self._create_mock_args(skip_assets_on=["big-repo"])
+        args = create_args(skip_assets_on=["big-repo"])
         repository = self._create_mock_repository(name="big-repo")
         release = self._create_mock_release()
 
@@ -180,10 +134,10 @@ class TestSkipAssetsOnBehavior(TestSkipAssetsOn):
     @patch("github_backup.github_backup.mkdir_p")
     @patch("github_backup.github_backup.json_dump_if_changed")
     def test_assets_skipped_when_full_name_matches(
-        self, mock_json_dump, mock_mkdir, mock_retrieve, mock_download
+        self, mock_json_dump, mock_mkdir, mock_retrieve, mock_download, create_args
     ):
         """Assets should be skipped when owner/repo format matches."""
-        args = self._create_mock_args(skip_assets_on=["otheruser/big-repo"])
+        args = create_args(skip_assets_on=["otheruser/big-repo"])
         repository = self._create_mock_repository(name="big-repo", owner="otheruser")
         release = self._create_mock_release()
 
@@ -206,11 +160,11 @@ class TestSkipAssetsOnBehavior(TestSkipAssetsOn):
     @patch("github_backup.github_backup.mkdir_p")
     @patch("github_backup.github_backup.json_dump_if_changed")
     def test_case_insensitive_matching(
-        self, mock_json_dump, mock_mkdir, mock_retrieve, mock_download
+        self, mock_json_dump, mock_mkdir, mock_retrieve, mock_download, create_args
     ):
         """Skip matching should be case-insensitive."""
         # User types uppercase, repo name is lowercase
-        args = self._create_mock_args(skip_assets_on=["BIG-REPO"])
+        args = create_args(skip_assets_on=["BIG-REPO"])
         repository = self._create_mock_repository(name="big-repo")
         release = self._create_mock_release()
 
@@ -233,10 +187,10 @@ class TestSkipAssetsOnBehavior(TestSkipAssetsOn):
     @patch("github_backup.github_backup.mkdir_p")
     @patch("github_backup.github_backup.json_dump_if_changed")
     def test_multiple_skip_repos(
-        self, mock_json_dump, mock_mkdir, mock_retrieve, mock_download
+        self, mock_json_dump, mock_mkdir, mock_retrieve, mock_download, create_args
     ):
         """Multiple repos in skip list should all be skipped."""
-        args = self._create_mock_args(skip_assets_on=["repo1", "repo2", "repo3"])
+        args = create_args(skip_assets_on=["repo1", "repo2", "repo3"])
         repository = self._create_mock_repository(name="repo2")
         release = self._create_mock_release()
 
@@ -259,10 +213,10 @@ class TestSkipAssetsOnBehavior(TestSkipAssetsOn):
     @patch("github_backup.github_backup.mkdir_p")
     @patch("github_backup.github_backup.json_dump_if_changed")
     def test_release_metadata_still_saved_when_assets_skipped(
-        self, mock_json_dump, mock_mkdir, mock_retrieve, mock_download
+        self, mock_json_dump, mock_mkdir, mock_retrieve, mock_download, create_args
     ):
         """Release JSON should still be saved even when assets are skipped."""
-        args = self._create_mock_args(skip_assets_on=["big-repo"])
+        args = create_args(skip_assets_on=["big-repo"])
         repository = self._create_mock_repository(name="big-repo")
         release = self._create_mock_release()
 
@@ -287,10 +241,10 @@ class TestSkipAssetsOnBehavior(TestSkipAssetsOn):
     @patch("github_backup.github_backup.mkdir_p")
     @patch("github_backup.github_backup.json_dump_if_changed")
     def test_non_matching_repo_still_downloads_assets(
-        self, mock_json_dump, mock_mkdir, mock_retrieve, mock_download
+        self, mock_json_dump, mock_mkdir, mock_retrieve, mock_download, create_args
     ):
         """Repos not in skip list should still download assets."""
-        args = self._create_mock_args(skip_assets_on=["other-repo"])
+        args = create_args(skip_assets_on=["other-repo"])
         repository = self._create_mock_repository(name="normal-repo")
         release = self._create_mock_release()
         asset = self._create_mock_asset()