GRM-51: fix: API resilience with retry, idempotent releases, and graceful Vikunja errors

tests/unit/test_auto_merge.py

@@ -16,6 +16,7 @@ from scripts.ci.auto_merge import (
     has_approval_review,
     has_ready_to_merge_label,
     main,
+    run_cmd,
     validate_pr_title,
     validate_pr_title_matches_vikunja,
     wait_for_ci,
@@ -604,3 +605,66 @@ class TestMain:
         result = runner.invoke(main, ["GRM-19-fix", "GRM-19: Some task title", "owner/repo", "1"])
         assert result.exit_code == 0
         assert "squash-merged" in result.output
+
+    @patch.dict("os.environ", {"REPO_TOKEN": "tok"})
+    @patch("scripts.ci.auto_merge.validate_pr_title_matches_vikunja")
+    @patch("scripts.ci.auto_merge.has_approval_review", return_value=True)
+    @patch("scripts.ci.auto_merge.GiteaClient")
+    def test_merge_405_behind_retries(
+        self, mock_client_cls: MagicMock, mock_approval: MagicMock, mock_vikunja: MagicMock
+    ) -> None:
+        """405 'behind' error should trigger rebase and retry."""
+        mock_client = MagicMock()
+        mock_client.get_pr_labels.return_value = [{"name": "ready-to-merge"}]
+        mock_client.get_pr.return_value = _mock_pr()
+        mock_client.get_commit_status.return_value = _mock_ci_passing()
+        mock_client.get_pr_commits.return_value = _mock_commits()
+        # First merge_pr raises 405 "behind", second succeeds
+        mock_client.merge_pr.side_effect = [
+            APIError(http.HTTPStatus.METHOD_NOT_ALLOWED, "head branch is behind base"),
+            None,
+        ]
+        mock_client_cls.return_value = mock_client
+        with patch("scripts.ci.auto_merge.run_cmd") as mock_run_cmd:
+            mock_run_cmd.return_value = MagicMock(returncode=0, stdout="", stderr="")
+            runner = CliRunner()
+            result = runner.invoke(main, ["GRM-19-fix", "GRM-19: Some task title", "owner/repo", "1"])
+            assert result.exit_code == 0
+            assert "Rebased" in result.output or "rebase" in result.output.lower()
+            assert mock_client.merge_pr.call_count == 2
+
+    @patch.dict("os.environ", {"REPO_TOKEN": "tok"})
+    @patch("scripts.ci.auto_merge.validate_pr_title_matches_vikunja")
+    @patch("scripts.ci.auto_merge.has_approval_review", return_value=True)
+    @patch("scripts.ci.auto_merge.GiteaClient")
+    def test_merge_405_behind_rebase_fails(
+        self, mock_client_cls: MagicMock, mock_approval: MagicMock, mock_vikunja: MagicMock
+    ) -> None:
+        """405 'behind' with rebase failure should raise ClickException."""
+        mock_client = MagicMock()
+        mock_client.get_pr_labels.return_value = [{"name": "ready-to-merge"}]
+        mock_client.get_pr.return_value = _mock_pr()
+        mock_client.get_commit_status.return_value = _mock_ci_passing()
+        mock_client.get_pr_commits.return_value = _mock_commits()
+        mock_client.merge_pr.side_effect = APIError(http.HTTPStatus.METHOD_NOT_ALLOWED, "head branch is behind base")
+        mock_client_cls.return_value = mock_client
+        with patch("scripts.ci.auto_merge.run_cmd") as mock_run_cmd:
+            mock_run_cmd.side_effect = click.ClickException("rebase failed")
+            runner = CliRunner()
+            result = runner.invoke(main, ["GRM-19-fix", "GRM-19: Some task title", "owner/repo", "1"])
+            assert result.exit_code == 1
+            assert "rebase" in result.output.lower() or "retry" in result.output.lower()
+
+    def test_run_cmd_success(self) -> None:
+        """run_cmd should return CompletedProcess on success."""
+        with patch("scripts.ci.auto_merge.subprocess.run") as mock_run:
+            mock_run.return_value = MagicMock(returncode=0, stdout="ok", stderr="")
+            result = run_cmd(["echo", "ok"])
+            assert result.returncode == 0
+
+    def test_run_cmd_failure_raises(self) -> None:
+        """run_cmd should raise ClickException on non-zero exit."""
+        with patch("scripts.ci.auto_merge.subprocess.run") as mock_run:
+            mock_run.return_value = MagicMock(returncode=1, stdout="", stderr="error")
+            with pytest.raises(click.ClickException):
+                run_cmd(["false"])