When you're migrating a codebase between framework versions or doing major refactors, this generates GitHub Copilot instructions by analyzing the diff between two git references. It creates a `.github/copilot-migration-instructions.md` file with transformation rules, API mappings, and before/after code examples so Copilot can automatically apply the same patterns to future changes. Works well for Angular upgrades, React class-to-hooks migrations, or architecture refactoring where you want Copilot to learn your specific transformation decisions. The real value is turning your one-time migration work into reusable automation rules.
npx skills add https://github.com/github/awesome-copilot --skill generate-custom-instructions-from-codebase