feat(tools): repo_tree, repo_topics_update, file_read dir fix (#14, #15, #18)

repo_tree: GET /git/trees/{ref}?recursive=1 — full recursive file tree
repo_topics_update: PUT /repos/{owner}/{repo}/topics — replace topic list
file_read: detect array response and return descriptive error for dir paths

internal/gitea/files.go

@@ -27,6 +27,10 @@ func (c *Client) GetFileContents(ctx context.Context, owner, repo, path, ref str
 	if err := MapStatus(status, body); err != nil {
 		return nil, err
 	}
+	// Array response means path is a directory — guide caller to dir_list.
+	if len(body) > 0 && body[0] == '[' {
+		return nil, fmt.Errorf("%w: path %q is a directory, not a file — use dir_list", ErrValidation, path)
+	}
 	var fc FileContents
 	if err := json.Unmarshal(body, &fc); err != nil {
 		return nil, err

internal/gitea/repos.go

@@ -18,6 +18,56 @@ type Repo struct {
 	Template      bool   `json:"template"`
 }
 
+type TreeEntry struct {
+	Path string `json:"path"`
+	Type string `json:"type"` // "blob" or "tree"
+	SHA  string `json:"sha"`
+	Size int64  `json:"size"`
+	URL  string `json:"url"`
+}
+
+type Tree struct {
+	SHA       string      `json:"sha"`
+	URL       string      `json:"url"`
+	Tree      []TreeEntry `json:"tree"`
+	Truncated bool        `json:"truncated"`
+}
+
+func (c *Client) GetTree(ctx context.Context, owner, repo, ref string, recursive bool) (*Tree, error) {
+	path := fmt.Sprintf("/api/v1/repos/%s/%s/git/trees/%s", owner, repo, url.PathEscape(ref))
+	if recursive {
+		path += "?recursive=1"
+	}
+	body, status, err := c.GetJSON(ctx, path)
+	if err != nil {
+		return nil, err
+	}
+	if err := MapStatus(status, body); err != nil {
+		return nil, err
+	}
+	var t Tree
+	if err := json.Unmarshal(body, &t); err != nil {
+		return nil, err
+	}
+	return &t, nil
+}
+
+func (c *Client) UpdateTopics(ctx context.Context, owner, repo string, topics []string) error {
+	path := fmt.Sprintf("/api/v1/repos/%s/%s/topics", owner, repo)
+	body, err := json.Marshal(map[string][]string{"topics": topics})
+	if err != nil {
+		return err
+	}
+	resp, status, err := c.PutJSON(ctx, path, body)
+	if err != nil {
+		return err
+	}
+	if status == 204 {
+		return nil
+	}
+	return MapStatus(status, resp)
+}
+
 func (c *Client) ListRepos(ctx context.Context, owner string, page, limit int) ([]Repo, error) {
 	if page < 1 {
 		page = 1

internal/gitea/repos_test.go

@@ -104,6 +104,38 @@ func TestUpdateRepo(t *testing.T) {
 	assert.Equal(t, "updated", r.Description)
 }
 
+func TestGetTree(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		assert.Equal(t, "/api/v1/repos/mathias/infra/git/trees/main", r.URL.Path)
+		assert.Equal(t, "1", r.URL.Query().Get("recursive"))
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(`{"sha":"abc","url":"http://x","tree":[{"path":"README.md","type":"blob","sha":"def","size":13},{"path":"internal","type":"tree","sha":"ghi"}],"truncated":false}`))
+	}))
+	defer srv.Close()
+
+	c := gitea.NewClient(srv.URL, "tok")
+	tree, err := c.GetTree(context.Background(), "mathias", "infra", "main", true)
+	require.NoError(t, err)
+	assert.Equal(t, "abc", tree.SHA)
+	require.Len(t, tree.Tree, 2)
+	assert.Equal(t, "README.md", tree.Tree[0].Path)
+	assert.Equal(t, "blob", tree.Tree[0].Type)
+	assert.Equal(t, int64(13), tree.Tree[0].Size)
+}
+
+func TestUpdateTopics(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		assert.Equal(t, http.MethodPut, r.Method)
+		assert.Equal(t, "/api/v1/repos/mathias/infra/topics", r.URL.Path)
+		w.WriteHeader(http.StatusNoContent)
+	}))
+	defer srv.Close()
+
+	c := gitea.NewClient(srv.URL, "tok")
+	err := c.UpdateTopics(context.Background(), "mathias", "infra", []string{"go", "mcp", "gitops"})
+	require.NoError(t, err)
+}
+
 func TestDefaultBranchCachesAcrossCalls(t *testing.T) {
 	var hits int32
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {