fix(ci): create dep-PR branches via POST /branches

Gitea lacks the POST /git/refs endpoint (HTTP 405). Use the branches
API with new_branch_name/old_branch_name; tolerate already-exists.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

tests/unit/test_create_dependency_pr.py

@@ -462,10 +462,10 @@ class TestCliManifestMode:
         assert args[1:4] == ("oblachno", "sso-bridge", "0.2.4")
 
 
-class TestMasterRefParsing:
-    """Gitea's /git/refs/heads/<branch> returns a list, not an object."""
+class TestBranchCreation:
+    """Branch creation uses the branches API (Gitea lacks POST /git/refs)."""
 
-    def _invoke(self, client: MagicMock) -> object:
+    def _invoke(self) -> object:
         runner = CliRunner()
         return runner.invoke(
             cli,
@@ -481,31 +481,10 @@ class TestMasterRefParsing:
             ],
         )
 
-    @patch("devx.ci.create_dependency_pr.create_vikunja_task", return_value=None)
-    @patch("devx.ci.create_dependency_pr.update_manifest", return_value=True)
-    @patch("devx.ci.create_dependency_pr.read_manifest_version", return_value="0.9.0")
-    @patch("devx.ci.create_dependency_pr.find_existing_pr", return_value=None)
-    @patch("devx.ci.create_dependency_pr.GiteaClient")
-    @patch("devx.ci.create_dependency_pr.get_ci_token", return_value="tok")
-    def test_list_shaped_ref_response(
-        self,
-        _token: MagicMock,
-        mock_client_cls: MagicMock,
-        _find: MagicMock,
-        _read: MagicMock,
-        _update: MagicMock,
-        _task: MagicMock,
-    ) -> None:
+    def _client(self, mock_client_cls: MagicMock) -> MagicMock:
         client = mock_client_cls.return_value
-        resp = MagicMock()
-        resp.json.return_value = [{"ref": "refs/heads/master", "object": {"sha": "abc123"}}]
-        client._request.return_value = resp
         client.create_pr.return_value = {"number": 1}
-        result = self._invoke(client)
-        assert result.exit_code == 0
-        assert "Created PR" in result.output
-        post = client._request.call_args_list[-1]
-        assert post.kwargs["json"]["sha"] == "abc123"
+        return client
 
     @patch("devx.ci.create_dependency_pr.create_vikunja_task", return_value=None)
     @patch("devx.ci.create_dependency_pr.update_manifest", return_value=True)
@@ -513,7 +492,7 @@ class TestMasterRefParsing:
     @patch("devx.ci.create_dependency_pr.find_existing_pr", return_value=None)
     @patch("devx.ci.create_dependency_pr.GiteaClient")
     @patch("devx.ci.create_dependency_pr.get_ci_token", return_value="tok")
-    def test_empty_ref_list_fails(
+    def test_creates_branch_via_branches_api(
         self,
         _token: MagicMock,
         mock_client_cls: MagicMock,
@@ -522,10 +501,59 @@ class TestMasterRefParsing:
         _update: MagicMock,
         _task: MagicMock,
     ) -> None:
-        client = mock_client_cls.return_value
-        resp = MagicMock()
-        resp.json.return_value = []
-        client._request.return_value = resp
-        result = self._invoke(client)
+        client = self._client(mock_client_cls)
+        result = self._invoke()
+        assert result.exit_code == 0
+        assert "Created PR" in result.output
+        post = client._request.call_args
+        assert post.args[:2] == ("POST", "/branches")
+        assert post.kwargs["json"] == {
+            "new_branch_name": "deps/sso_bridge-0.9.1",
+            "old_branch_name": "master",
+        }
+
+    @patch("devx.ci.create_dependency_pr.create_vikunja_task", return_value=None)
+    @patch("devx.ci.create_dependency_pr.update_manifest", return_value=True)
+    @patch("devx.ci.create_dependency_pr.read_manifest_version", return_value="0.9.0")
+    @patch("devx.ci.create_dependency_pr.find_existing_pr", return_value=None)
+    @patch("devx.ci.create_dependency_pr.GiteaClient")
+    @patch("devx.ci.create_dependency_pr.get_ci_token", return_value="tok")
+    def test_existing_branch_tolerated(
+        self,
+        _token: MagicMock,
+        mock_client_cls: MagicMock,
+        _find: MagicMock,
+        _read: MagicMock,
+        _update: MagicMock,
+        _task: MagicMock,
+    ) -> None:
+        from devx.exceptions import APIError
+
+        client = self._client(mock_client_cls)
+        client._request.side_effect = APIError(422, "branch already exists")
+        result = self._invoke()
+        assert result.exit_code == 0
+        assert "already exists" in result.output.lower()
+
+    @patch("devx.ci.create_dependency_pr.create_vikunja_task", return_value=None)
+    @patch("devx.ci.create_dependency_pr.update_manifest", return_value=True)
+    @patch("devx.ci.create_dependency_pr.read_manifest_version", return_value="0.9.0")
+    @patch("devx.ci.create_dependency_pr.find_existing_pr", return_value=None)
+    @patch("devx.ci.create_dependency_pr.GiteaClient")
+    @patch("devx.ci.create_dependency_pr.get_ci_token", return_value="tok")
+    def test_branch_api_error_fails(
+        self,
+        _token: MagicMock,
+        mock_client_cls: MagicMock,
+        _find: MagicMock,
+        _read: MagicMock,
+        _update: MagicMock,
+        _task: MagicMock,
+    ) -> None:
+        from devx.exceptions import APIError
+
+        client = self._client(mock_client_cls)
+        client._request.side_effect = APIError(500, "boom")
+        result = self._invoke()
         assert result.exit_code != 0
-        assert "master SHA" in str(result.exception) or "master SHA" in result.output
+        assert "Failed to create branch" in result.output