Add ability to view branches for a repo #141 (#205)

* Add ability to view branches for a repo #141

* fix: update ListBranches test to use InputSchema and correct translation helper

* fix: update ListBranches test to use InputSchema and correct translation helper

* fix: update ListBranches test to handle errors in tool result

* fix: replace deprecated github.String with github.Ptr

* docs: add list_branches tool documentation to README

Author: aryasoni98

README.md

@@ -311,6 +311,13 @@ export GITHUB_MCP_TOOL_ADD_ISSUE_COMMENT_DESCRIPTION="an alternative description
   - `branch`: Branch name (string, optional)
   - `sha`: File SHA if updating (string, optional)
 
+- **list_branches** - List branches in a GitHub repository
+
+  - `owner`: Repository owner (string, required)
+  - `repo`: Repository name (string, required)
+  - `page`: Page number (number, optional)
+  - `perPage`: Results per page (number, optional)
+
 - **push_files** - Push multiple files in a single commit
 
   - `owner`: Repository owner (string, required)

pkg/github/repositories.go

@@ -150,6 +150,69 @@ func ListCommits(getClient GetClientFn, t translations.TranslationHelperFunc) (t
 		}
 }
 
+// ListBranches creates a tool to list branches in a GitHub repository.
+func ListBranches(getClient GetClientFn, t translations.TranslationHelperFunc) (tool mcp.Tool, handler server.ToolHandlerFunc) {
+	return mcp.NewTool("list_branches",
+			mcp.WithDescription(t("TOOL_LIST_BRANCHES_DESCRIPTION", "List branches in a GitHub repository")),
+			mcp.WithString("owner",
+				mcp.Required(),
+				mcp.Description("Repository owner"),
+			),
+			mcp.WithString("repo",
+				mcp.Required(),
+				mcp.Description("Repository name"),
+			),
+			WithPagination(),
+		),
+		func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+			owner, err := requiredParam[string](request, "owner")
+			if err != nil {
+				return mcp.NewToolResultError(err.Error()), nil
+			}
+			repo, err := requiredParam[string](request, "repo")
+			if err != nil {
+				return mcp.NewToolResultError(err.Error()), nil
+			}
+			pagination, err := OptionalPaginationParams(request)
+			if err != nil {
+				return mcp.NewToolResultError(err.Error()), nil
+			}
+
+			opts := &github.BranchListOptions{
+				ListOptions: github.ListOptions{
+					Page:    pagination.page,
+					PerPage: pagination.perPage,
+				},
+			}
+
+			client, err := getClient(ctx)
+			if err != nil {
+				return nil, fmt.Errorf("failed to get GitHub client: %w", err)
+			}
+
+			branches, resp, err := client.Repositories.ListBranches(ctx, owner, repo, opts)
+			if err != nil {
+				return nil, fmt.Errorf("failed to list branches: %w", err)
+			}
+			defer func() { _ = resp.Body.Close() }()
+
+			if resp.StatusCode != http.StatusOK {
+				body, err := io.ReadAll(resp.Body)
+				if err != nil {
+					return nil, fmt.Errorf("failed to read response body: %w", err)
+				}
+				return mcp.NewToolResultError(fmt.Sprintf("failed to list branches: %s", string(body))), nil
+			}
+
+			r, err := json.Marshal(branches)
+			if err != nil {
+				return nil, fmt.Errorf("failed to marshal response: %w", err)
+			}
+
+			return mcp.NewToolResultText(string(r)), nil
+		}
+}
+
 // CreateOrUpdateFile creates a tool to create or update a file in a GitHub repository.
 func CreateOrUpdateFile(getClient GetClientFn, t translations.TranslationHelperFunc) (tool mcp.Tool, handler server.ToolHandlerFunc) {
 	return mcp.NewTool("create_or_update_file",

pkg/github/repositories_test.go

@@ -1423,3 +1423,113 @@ func Test_PushFiles(t *testing.T) {
 		})
 	}
 }
+
+func Test_ListBranches(t *testing.T) {
+	// Verify tool definition once
+	mockClient := github.NewClient(nil)
+	tool, _ := ListBranches(stubGetClientFn(mockClient), translations.NullTranslationHelper)
+
+	assert.Equal(t, "list_branches", tool.Name)
+	assert.NotEmpty(t, tool.Description)
+	assert.Contains(t, tool.InputSchema.Properties, "owner")
+	assert.Contains(t, tool.InputSchema.Properties, "repo")
+	assert.Contains(t, tool.InputSchema.Properties, "page")
+	assert.Contains(t, tool.InputSchema.Properties, "perPage")
+	assert.ElementsMatch(t, tool.InputSchema.Required, []string{"owner", "repo"})
+
+	// Setup mock branches for success case
+	mockBranches := []*github.Branch{
+		{
+			Name:   github.Ptr("main"),
+			Commit: &github.RepositoryCommit{SHA: github.Ptr("abc123")},
+		},
+		{
+			Name:   github.Ptr("develop"),
+			Commit: &github.RepositoryCommit{SHA: github.Ptr("def456")},
+		},
+	}
+
+	// Test cases
+	tests := []struct {
+		name          string
+		args          map[string]interface{}
+		mockResponses []mock.MockBackendOption
+		wantErr       bool
+		errContains   string
+	}{
+		{
+			name: "success",
+			args: map[string]interface{}{
+				"owner": "owner",
+				"repo":  "repo",
+				"page":  float64(2),
+			},
+			mockResponses: []mock.MockBackendOption{
+				mock.WithRequestMatch(
+					mock.GetReposBranchesByOwnerByRepo,
+					mockBranches,
+				),
+			},
+			wantErr: false,
+		},
+		{
+			name: "missing owner",
+			args: map[string]interface{}{
+				"repo": "repo",
+			},
+			mockResponses: []mock.MockBackendOption{},
+			wantErr:       false,
+			errContains:   "missing required parameter: owner",
+		},
+		{
+			name: "missing repo",
+			args: map[string]interface{}{
+				"owner": "owner",
+			},
+			mockResponses: []mock.MockBackendOption{},
+			wantErr:       false,
+			errContains:   "missing required parameter: repo",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Create mock client
+			mockClient := github.NewClient(mock.NewMockedHTTPClient(tt.mockResponses...))
+			_, handler := ListBranches(stubGetClientFn(mockClient), translations.NullTranslationHelper)
+
+			// Create request
+			request := createMCPRequest(tt.args)
+
+			// Call handler
+			result, err := handler(context.Background(), request)
+			if tt.wantErr {
+				require.Error(t, err)
+				if tt.errContains != "" {
+					assert.Contains(t, err.Error(), tt.errContains)
+				}
+				return
+			}
+
+			require.NoError(t, err)
+			require.NotNil(t, result)
+
+			if tt.errContains != "" {
+				textContent := getTextResult(t, result)
+				assert.Contains(t, textContent.Text, tt.errContains)
+				return
+			}
+
+			textContent := getTextResult(t, result)
+			require.NotEmpty(t, textContent.Text)
+
+			// Verify response
+			var branches []*github.Branch
+			err = json.Unmarshal([]byte(textContent.Text), &branches)
+			require.NoError(t, err)
+			assert.Len(t, branches, 2)
+			assert.Equal(t, "main", *branches[0].Name)
+			assert.Equal(t, "develop", *branches[1].Name)
+		})
+	}
+}

pkg/github/server.go

@@ -70,6 +70,7 @@ func NewServer(getClient GetClientFn, version string, readOnly bool, t translati
 	s.AddTool(GetFileContents(getClient, t))
 	s.AddTool(GetCommit(getClient, t))
 	s.AddTool(ListCommits(getClient, t))
+	s.AddTool(ListBranches(getClient, t))
 	if !readOnly {
 		s.AddTool(CreateOrUpdateFile(getClient, t))
 		s.AddTool(CreateRepository(getClient, t))