# Git Diff Explainer CLI

A CLI tool that parses git diffs and provides intelligent, contextual explanations of code changes. Identifies programming language, summarizes changes, flags potential issues, and suggests improvements - all running locally without external API dependencies.

## Features

- **Parse git diffs/patches**: Extract file names, hunks, and code changes from unified diff format
- **Identify programming language**: Detect language from file extensions and code patterns
- **Summarize changes**: Generate human-readable summaries of what each change does
- **Flag potential issues**: Detect bugs, security vulnerabilities, and code smells
- **Suggest improvements**: Provide specific refactoring suggestions
- **Local execution**: Runs entirely offline using local libraries
- **Color-coded output**: Terminal output with ANSI colors for better readability

## Installation

```bash
# Using pip
pip install git-diff-explainer-cli

# From source
git clone <repository>
cd git-diff-explainer-cli
pip install -e .
```

## Usage

### Basic Usage

```bash
# Explain a diff from stdin
git diff | gdiffer explain --stdin

# Explain a diff file
gdiffer explain --file changes.diff

# Pass diff as argument
gdiffer explain "diff --git a/file.py b/file.py..."

# Get just the summary
gdiffer summarize --file changes.diff

# Check for issues only
gdiffer issues --file changes.diff
```

### Options

```bash
# Output format: terminal (default), json, plain
gdiffer explain --output json

# Verbose output
gdiffer explain --verbose
```

## Examples

### Simple Diff Explanation

```bash
$ git diff | gdiffer explain
=== Git Diff Analysis Summary ===
Total files changed: 1
Files added: 0
Files deleted: 0
Files modified: 1
Total changes: 3

Languages:
  - python: 1 files

=== File Changes ===

1. src/main.py
   Status: modify
   Changes: 3 lines
   Hunk 1:
    +import os
    +import sys
    def main():
        print("Hello, World!")
```

### JSON Output

```bash
$ gdiffer explain --output json "diff --git a/test.py..."
{
  "summary": {
    "total_files": 1,
    "files_added": 0,
    "files_deleted": 0,
    "files_modified": 1,
    "total_changes": 2
  },
  "files": [...]
}
```

### Issue Detection

```bash
$ gdiffer issues --file sql_injection.diff
[CRITICAL] Potential SQL Injection
  File: db.py:5
  Description: String concatenation or interpolation used in SQL query
  Suggestion: Use parameterized queries or ORM methods
```

## Supported Languages

- Python
- JavaScript / TypeScript
- Java
- Go
- Rust
- C / C++
- Ruby
- PHP
- And more...

## Configuration

Environment variables:

| Variable | Description | Default |
|----------|-------------|---------|
| `GDIFF_OUTPUT` | Output format: terminal, json, plain | terminal |
| `GDIFF_VERBOSE` | Enable verbose output | false |

## Development

```bash
# Install development dependencies
pip install -e ".[dev]"

# Run tests
pytest tests/ -v

# Run with coverage
pytest tests/ --cov=src/gdiffer

# Type checking
mypy src/gdiffer/

# Linting
ruff check src/gdiffer/
```

## Error Handling

Common errors and solutions:

| Error | Solution |
|-------|----------|
| Invalid git diff format | Provide a valid unified diff format |
| No changes detected | Ensure the diff contains actual code changes |
| Unsupported language | Use a supported language or file extension |

## License

MIT