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Generate Custom Instructions From Codebase

GitHubOfficialOriginally contributed by @AClerbois as prompts/generate-custom-instructions-from-codebase.prompt.md; moved into a skill by pull request #761Distributed by GitHub

  • Skill
  • Content generator
  • Software development
  • MIT
  • No issues found

From the author

Migration and code evolution instructions generator for GitHub Copilot. Analyzes differences between two project versions (branches, commits, or releases) to create precise instructions allowing Copilot to maintain consistency during technology migrations, major refactoring, or framework version upgrades.
— the description by AClerbois

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

This skill analyzes the differences between two versions of a codebase—such as branches, commits, or tags—to produce a structured set of migration instructions. By documenting transformation patterns, API changes, and architectural shifts, it creates a guide that helps GitHub Copilot maintain consistency and apply correct patterns during future development, refactoring, or framework upgrades.

What it does

  • Compares two project states to identify structural and code-level changes.
  • Extracts transformation patterns and API correspondences from codebase evolution.
  • Generates a structured markdown file containing migration rules for GitHub Copilot.
  • Provides before-and-after code examples to illustrate required transformations.
  • Defines validation criteria and control points for automated migration tasks.
  • Documents obsolete patterns to prevent their reintroduction.

When to use it

  • During framework version upgrades (e.g., migrating between major versions).
  • When performing large-scale architectural refactoring.
  • During technology stack migrations (e.g., replacing a library or language).
  • When adopting new design patterns or coding conventions across a project.

Advantages

  • Trains GitHub Copilot to reproduce specific project evolution decisions.
  • Capitalizes on migration expertise by turning it into reusable rules.
  • Ensures consistency by providing context-aware instructions tailored to the codebase.
  • Reduces manual effort and errors during repetitive transformation tasks.
  • Prevents architectural regression by enforcing new conventions.

Usage examples

“Generate migration instructions for upgrading our project from React 16 to React 18, focusing on API changes.”
A markdown file detailing the transformation rules for hooks, component updates, and API replacements to guide Copilot.
“Create refactoring instructions for moving our codebase from a monolithic structure to a modular architecture.”
A set of instructions identifying new abstractions and data flow changes to help Copilot suggest consistent code structures.

Install

  1. Download the skill as a ZIP:

    https://autogineer.com/agent-skills/github/generate-custom-instructions-from-codebase/download
  2. Unzip it into the cross-client skills folder of your project:

    mkdir -p .agents/skills && unzip generate-custom-instructions-from-codebase.zip -d .agents/skills

Documentation by AClerbois

Migration and Code Evolution Instructions Generator

Configuration Variables

${MIGRATION_TYPE="Framework Version|Architecture Refactoring|Technology Migration|Dependencies Update|Pattern Changes"}
<!-- Type of migration or evolution -->

${SOURCE_REFERENCE="branch|commit|tag"}
<!-- Source reference point (before state) -->

${TARGET_REFERENCE="branch|commit|tag"}  
<!-- Target reference point (after state) -->

${ANALYSIS_SCOPE="Entire project|Specific folder|Modified files only"}
<!-- Scope of analysis -->

${CHANGE_FOCUS="Breaking Changes|New Conventions|Obsolete Patterns|API Changes|Configuration"}
<!-- Main aspect of changes -->

${AUTOMATION_LEVEL="Conservative|Balanced|Aggressive"}
<!-- Level of automation for Copilot suggestions -->

${GENERATE_EXAMPLES="true|false"}
<!-- Include transformation examples -->

${VALIDATION_REQUIRED="true|false"}
<!-- Require validation before application -->

Generated Prompt

"Analyze code evolution between two project states to generate precise migration instructions for GitHub Copilot. These instructions will guide Copilot to automatically apply the same transformation patterns during future modifications. Follow this methodology:

### Phase 1: Comparative State Analysis

#### Structural Changes Detection
- Compare folder structure between ${SOURCE_REFERENCE} and ${TARGET_REFERENCE}
- Identify moved, renamed, or deleted files
- Analyze changes in configuration files
- Document new dependencies and removed ones

#### Code Transformation Analysis
${MIGRATION_TYPE == "Framework Version" ? 
  "- Identify API changes between framework versions
   - Analyze new features being used
   - Document obsolete methods/properties
   - Note syntax or convention changes" : ""}

${MIGRATION_TYPE == "Architecture Refactoring" ? 
  "- Analyze architectural pattern changes
   - Identify new abstractions introduced
   - Document responsibility reorganization
   - Note changes in data flows" : ""}

${MIGRATION_TYPE == "Technology Migration" ? 
  "- Analyze replacement of one technology with another
   - Identify functional equivalences
   - Document API and syntax changes
   - Note new dependencies and configurations" : ""}

#### Transformation Pattern Extraction
- Identify repetitive transformations applied
- Analyze conversion rules from old to new format
- Document exceptions and special cases
- Create before/after correspondence matrix

### Phase 2: Migration Instructions Generation

Create a `.github/copilot-migration-instructions.md` file with this structure:

\`\`\`markdown
# GitHub Copilot Migration Instructions

## Migration Context
- **Type**: ${MIGRATION_TYPE}
- **From**: ${SOURCE_REFERENCE} 
- **To**: ${TARGET_REFERENCE}
- **Date**: [GENERATION_DATE]
- **Scope**: ${ANALYSIS_SCOPE}

## Automatic Transformation Rules

### 1. Mandatory Transformations
${AUTOMATION_LEVEL != "Conservative" ? 
  "[AUTOMATIC_TRANSFORMATION_RULES]
   - **Old Pattern**: [OLD_CODE]
   - **New Pattern**: [NEW_CODE]
   - **Trigger**: When to detect this pattern
   - **Action**: Transformation to apply automatically" : ""}

### 2. Transformations with Validation
${VALIDATION_REQUIRED == "true" ? 
  "[TRANSFORMATIONS_WITH_VALIDATION]
   - **Detected Pattern**: [DESCRIPTION]
   - **Suggested Transformation**: [NEW_APPROACH]
   - **Required Validation**: [VALIDATION_CRITERIA]
   - **Alternatives**: [ALTERNATIVE_OPTIONS]" : ""}

### 3. API Correspondences
${CHANGE_FOCUS == "API Changes" || MIGRATION_TYPE == "Framework Version" ? 
  "[API_CORRESPONDENCE_TABLE]
   | Old API   | New API   | Notes     | Example        |
   | --------- | --------- | --------- | -------------- |
   | [OLD_API] | [NEW_API] | [CHANGES] | [CODE_EXAMPLE] | " : ""} |

### 4. New Patterns to Adopt
[DETECTED_EMERGING_PATTERNS]
- **Pattern**: [PATTERN_NAME]
- **Usage**: [WHEN_TO_USE] 
- **Implementation**: [HOW_TO_IMPLEMENT]
- **Benefits**: [ADVANTAGES]

### 5. Obsolete Patterns to Avoid
[DETECTED_OBSOLETE_PATTERNS]
- **Obsolete Pattern**: [OLD_PATTERN]
- **Why Avoid**: [REASONS]
- **Alternative**: [NEW_PATTERN]
- **Migration**: [CONVERSION_STEPS]

## File Type Specific Instructions

${GENERATE_EXAMPLES == "true" ? 
  "### Configuration Files
   [CONFIG_TRANSFORMATION_EXAMPLES]
   
   ### Main Source Files
   [SOURCE_TRANSFORMATION_EXAMPLES]
   
   ### Test Files
   [TEST_TRANSFORMATION_EXAMPLES]" : ""}

## Validation and Security

### Automatic Control Points
- Verifications to perform after each transformation
- Tests to run to validate changes
- Performance metrics to monitor
- Compatibility checks to perform

### Manual Escalation
Situations requiring human intervention:
- [COMPLEX_CASES_LIST]
- [ARCHITECTURAL_DECISIONS]
- [BUSINESS_IMPACTS]

## Migration Monitoring

### Tracking Metrics
- Percentage of code automatically migrated
- Number of manual validations required
- Error rate of automatic transformations
- Average migration time per file

### Error Reporting
How to report incorrect transformations to Copilot:
- Feedback patterns to improve rules
- Exceptions to document
- Adjustments to make to instructions

\`\`\`

### Phase 3: Contextual Examples Generation

${GENERATE_EXAMPLES == "true" ? 
  "#### Transformation Examples
   For each identified pattern, generate:
   
   \`\`\`
   // BEFORE (${SOURCE_REFERENCE})
   [OLD_CODE_EXAMPLE]
   
   // AFTER (${TARGET_REFERENCE}) 
   [NEW_CODE_EXAMPLE]
   
   // COPILOT INSTRUCTIONS
   When you see this pattern [TRIGGER], transform it to [NEW_PATTERN] following these steps: [STEPS]
   \`\`\`" : ""}

### Phase 4: Validation and Optimization

#### Instructions Testing
- Apply instructions on test code
- Verify transformation consistency
- Adjust rules based on results
- Document exceptions and edge cases

#### Iterative Optimization  
${AUTOMATION_LEVEL == "Aggressive" ? 
  "- Refine rules to maximize automation
   - Reduce false positives in detection
   - Improve transformation accuracy
   - Document lessons learned" : ""}

### Final Result

Migration instructions that enable GitHub Copilot to:
1. **Automatically apply** the same transformations during future modifications
2. **Maintain consistency** with newly adopted conventions  
3. **Avoid obsolete patterns** by automatically proposing alternatives
4. **Accelerate future migrations** by capitalizing on acquired experience
5. **Reduce errors** by automating repetitive transformations

These instructions transform Copilot into an intelligent migration assistant, capable of reproducing your technology evolution decisions consistently and reliably.
"

Typical Use Cases

Framework Version Migration

Perfect for documenting the transition from Angular 14 to Angular 17, React Class Components to Hooks, or .NET Framework to .NET Core. Automatically identifies breaking changes and generates corresponding transformation rules.

Technology Stack Evolution

Essential when replacing a technology entirely: jQuery to React, REST to GraphQL, SQL to NoSQL. Creates a comprehensive migration guide with pattern mappings.

Architecture Refactoring

Ideal for large refactorings like Monolith to Microservices, MVC to Clean Architecture, or Component to Composable architecture. Preserves architectural knowledge for future similar transformations.

Design Pattern Modernization

Useful for adopting new patterns: Repository Pattern, Dependency Injection, Observer to Reactive Programming. Documents the rationale and implementation differences.

Unique Benefits

🧠 Artificial Intelligence Enhancement

Unlike traditional migration documentation, these instructions "train" GitHub Copilot to reproduce your technology evolution decisions automatically during future code modifications.

🔄 Knowledge Capitalization

Transforms specific project experience into reusable rules, avoiding the loss of migration expertise and accelerating future similar transformations.

🎯 Context-Aware Precision

Instead of generic advice, generates instructions tailored to your specific codebase, with real before/after examples from your project evolution.

⚡ Automated Consistency

Ensures that new code additions automatically follow the new conventions, preventing architectural regression and maintaining code evolution coherence.

Files

ATTRIBUTION.md

Attribution

This folder is an unmodified copy of the Agent Skill "generate-custom-instructions-from-codebase", distributed by AutoGineer (https://autogineer.com/agent-skills).

The skill's own files are unmodified copies. AutoGineer is not affiliated with or endorsed by the author or the publisher.

Files added by AutoGineer

  • ATTRIBUTION.md: this file, written by AutoGineer

  • LICENSE: copied from LICENSE

Requirements and compatibility

Written for: GitHub Copilot

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Security

No issues found by our static scan· No issues found

A static scan is not a guarantee. Skills are third-party content: review a skill before you let an agent use it.

Attribution and licence

Originally contributed by
GitHub avatar of AClerbois@AClerboisas prompts/generate-custom-instructions-from-codebase.prompt.mdmoved into a skill by pull request #761
Publisher
GitHub (Official)
Distributed by
GitHub
Source
github/awesome-copilot · skills/generate-custom-instructions-from-codebase · commit 797337f
Licence
MIT License (redistribution allowed)
  • LICENSE (added by AutoGineer from LICENSE)
  • ATTRIBUTION.md (written by AutoGineer)
Synced
Contributors
AClerbois

AutoGineer is not affiliated with or endorsed by AClerbois or GitHub.

Download ZIP

The ZIP holds the skill’s files, its licence files and an ATTRIBUTION.md. Download generate-custom-instructions-from-codebase.zip