This PR implements the necessary changes to optimize the codeql-development-toolkit repository for GitHub Copilot compatibility, enabling better assistance when assigning repository issues to the Copilot Coding Agent.

Changes Made

1. Custom Instructions for Copilot Agents

Added comprehensive instruction files in .github/instructions/ following GitHub's repository custom instructions guidelines:

• csharp.instructions.md: Provides C# coding patterns, architecture conventions, and project-specific guidance including:

  • Nullable reference type usage patterns
  • Feature-based architecture with BaseLifecycleTarget inheritance
  • Logging patterns using Log<ClassName>.G().LogInformation()
  • Template rendering with Scriban/Liquid templates
  • Testing conventions with NUnit

• liquid.instructions.md: Covers Liquid template structure and conventions for:

  • CodeQL query file generation with proper metadata headers
  • GitHub Actions workflow template patterns
  • Variable naming conventions (snake_case)
  • File path construction patterns for CodeQL projects

• repository.instructions.md: Provides high-level project context including:

  • Repository structure and key components
  • Development workflow and CLI usage patterns
  • Feature architecture and automation types
  • Contributing guidelines and testing approaches

2. Copilot Environment Pre-installation Workflow

Created .github/workflows/copilot-setup-steps.yml to pre-install dependencies required for effective Copilot assistance:

• Primary requirement: Installs .NET 6.0.x specifically needed for the qlt CLI tool
• System dependencies: Ensures GitHub CLI, unzip, and curl are available
• Validation steps: Verifies environment by building the project and testing QLT functionality
• Clear indicators: Provides success confirmations for Copilot environment readiness

The workflow runs on push/PR to main branch and can be manually triggered, ensuring the setup is validated in CI.

Validation

All changes have been thoroughly tested:

• ✅ Workflow YAML syntax validated
• ✅ .NET 6.0.x installation and QLT CLI functionality confirmed
• ✅ Full project build and test suite passes with .NET 6 runtime
• ✅ All system dependencies verified available
• ✅ End-to-end Copilot setup validation successful

These changes ensure GitHub Copilot agents have the necessary context and pre-installed dependencies to effectively assist with CodeQL development tasks in this repository.

Fixes #30.

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.