Add pagination support to get_pull_request_files tool

Fixes #527

Problem

The get_pull_request_files tool currently retrieves only the first 30 files with diffs of any PR that contains more than 30 files. This is a limitation because large PRs with many files cannot be fully analyzed.

Solution

Added pagination support to the get_pull_request_files tool by:

• Adding WithPagination() to the tool definition
• Using OptionalPaginationParams(request) to handle page and perPage parameters
• Passing pagination parameters to the GitHub API ListFiles call
• Following the same pattern used by other paginated tools in the codebase

Changes Made

1. Core Implementation (pkg/github/pullrequests.go)

// Added WithPagination() to tool definition
WithPagination(),

// Added pagination parameter handling
pagination, err := OptionalPaginationParams(request)
if err != nil {
    return mcp.NewToolResultError(err.Error()), nil
}

// Updated GitHub API call to use pagination
opts := &github.ListOptions{
    PerPage: pagination.perPage,
    Page:    pagination.page,
}

2. Test Updates (pkg/github/pullrequests_test.go)

• Added verification that pagination parameters (page, perPage) are present in tool schema
• Added test case for successful files fetch with pagination parameters
• Updated tool schema snapshot to reflect new parameters

3. Schema Snapshot (pkg/github/__toolsnaps__/get_pull_request_files.snap)

• Automatically updated to include new pagination parameters
• Ensures schema changes are tracked and validated

Testing Done

1. Unit Tests

# All tests pass
go test ./pkg/github -v

Test Results:

• ✅ Test_GetPullRequestFiles - All test cases pass including new pagination test
• ✅ Schema verification - Confirms page and perPage parameters are present
• ✅ Pagination functionality - Verifies tool works with pagination parameters

2. Integration Testing

# Verified tool schema includes pagination parameters
GITHUB_PERSONAL_ACCESS_TOKEN=xxx ./mcpcurl --stdio-server-cmd="./github-mcp-server stdio --toolsets pull_requests" schema

Schema Verification:

{
  "name": "get_pull_request_files",
  "inputSchema": {
    "properties": {
      "owner": {"description": "Repository owner", "type": "string"},
      "page": {"description": "Page number for pagination (min 1)", "minimum": 1, "type": "number"},
      "perPage": {"description": "Results per page for pagination (min 1, max 100)", "maximum": 100, "minimum": 1, "type": "number"},
      "pullNumber": {"description": "Pull request number", "type": "number"},
      "repo": {"description": "Repository name", "type": "string"}
    },
    "required": ["owner", "repo", "pullNumber"]
  }
}

3. GitHub API Verification

# Verified GitHub API supports pagination for PR files
curl -H "Authorization: token xxx" "https://api.github.com/repos/github/github-mcp-server/pulls/521/files?per_page=2&page=1"

API Response: Successfully returned paginated results with 2 files per page.

4. Build Verification

# Server builds successfully with changes
go build -o github-mcp-server cmd/github-mcp-server/main.go

Usage Examples

Default behavior (no pagination parameters):

{
  "owner": "github",
  "repo": "github-mcp-server", 
  "pullNumber": 123
}

With pagination:

{
  "owner": "github",
  "repo": "github-mcp-server",
  "pullNumber": 123,
  "page": 2,
  "perPage": 10
}

Backward Compatibility

• ✅ Fully backward compatible - Existing calls without pagination parameters work exactly as before
• ✅ Optional parameters - page and perPage are optional with sensible defaults
• ✅ Same response format - Returns the same JSON structure as before

Impact

• Large PRs: Can now analyze PRs with more than 30 files
• Performance: Users can control the number of files retrieved per request
• Flexibility: Supports both default behavior and custom pagination

Files Changed

• pkg/github/pullrequests.go - Core implementation
• pkg/github/pullrequests_test.go - Test updates
• pkg/github/__toolsnaps__/get_pull_request_files.snap - Schema snapshot