Polish customer update flow and prepare ZIP installation

tests/test_updater.py

@@ -48,11 +48,14 @@ class UpdaterTests(unittest.TestCase):
         self.git(self.author, "push", "origin", "main")
 
     def test_fast_forward_and_requirements_change(self):
+        self.assertFalse(updater.check_for_update()["update_available"])
         self.assertFalse(updater.update_package()["updated"])
         # The release URL, not the user's origin, determines the update source.
         self.git(self.install, "remote", "set-url", "origin", str(self.install / "unused-origin"))
         (self.author / "requirements.txt").write_text("requests>=3\n", encoding="utf-8")
         self.commit_and_push()
+        self.assertTrue(updater.check_for_update()["update_available"])
+        self.assertEqual((self.install / "requirements.txt").read_text(encoding="utf-8"), "requests>=2\n")
         result = updater.update_package()
         self.assertTrue(result["updated"])
         self.assertTrue(result["requirements_changed"])
@@ -60,6 +63,13 @@ class UpdaterTests(unittest.TestCase):
 
     def test_local_modification_is_preserved(self):
         (self.install / "version.txt").write_text("local work\n", encoding="utf-8")
+        self.assertFalse(updater.check_for_update()["update_available"])
+        self.assertFalse(updater.update_package()["updated"])
+        (self.author / "version.txt").write_text("new release\n", encoding="utf-8")
+        self.commit_and_push()
+        with self.assertRaises(updater.UpdateError) as caught:
+            updater.check_for_update()
+        self.assertEqual(caught.exception.code, "local_changes")
         with self.assertRaises(updater.UpdateError) as caught:
             updater.update_package()
         self.assertEqual(caught.exception.code, "local_changes")