feat: add Google Gemini provider support

.env.example

@@ -1,3 +1,7 @@
 # OpenAI API Key
 # Get yours at: https://platform.openai.com/api-keys
 OPENAI_API_KEY=sk-your-api-key-here
+
+# Gemini API Key
+# Get yours at: https://aistudio.google.com/u/1/api-keys
+GEMINI_API_KEY=gemini-api-key

package.json

@@ -47,16 +47,17 @@
     "LICENSE"
   ],
   "dependencies": {
-    "openai": "^4.20.0",
-    "commander": "^11.1.0",
+    "@google/generative-ai": "^0.24.1",
     "chalk": "^5.3.0",
-    "ora": "^7.0.1",
-    "node-fetch": "^3.3.2"
+    "commander": "^11.1.0",
+    "node-fetch": "^3.3.2",
+    "openai": "^4.20.0",
+    "ora": "^7.0.1"
   },
   "devDependencies": {
     "@types/node": "^20.10.0",
-    "typescript": "^5.3.2",
-    "tsx": "^4.6.2"
+    "tsx": "^4.6.2",
+    "typescript": "^5.3.2"
   },
   "publishConfig": {
     "access": "public"

src/cli.ts

@@ -133,6 +133,13 @@ async function installCommitHooks(): Promise<void> {
     console.log(chalk.gray('   npm install -g @anthropic-ai/claude-code'));
     console.log(chalk.gray('   claude login'));
     console.log(chalk.gray('   git config hooks.commitProvider claude-code'));
+    console.log(chalk.gray('\n   # Option D: Gemini (sends data to Google API)'));
+    if (isWindows) {
+      console.log(chalk.gray('   set GEMINI_API_KEY="your-api-key"'));
+    } else {
+      console.log(chalk.gray('   export GEMINI_API_KEY="your-api-key"'));
+    }
+    console.log(chalk.gray('   git config hooks.commitProvider gemini'));
 
     console.log('\n3. Optional customizations:');
     console.log(chalk.gray('   git config hooks.commitTemplate "type(scope): message"'));
@@ -148,9 +155,9 @@ program
   .name('git-rewrite-commits')
   .description('AI-powered git commit message rewriter using OpenAI or Ollama')
   .version(packageJson.version)
-  .option('--provider <provider>', 'AI provider to use: "openai", "ollama", or "claude-code"', 'openai')
-  .option('-k, --api-key <key>', 'OpenAI API key (defaults to OPENAI_API_KEY env var)')
-  .option('-m, --model <model>', 'AI model to use (default: gpt-3.5-turbo for OpenAI, llama3.2 for Ollama, haiku for Claude Code)')
+  .option('--provider <provider>', 'AI provider to use: "openai", "ollama", "claude-code", or "gemini"', 'openai')
+  .option('-k, --api-key <key>', 'API key for the selected provider (defaults to OPENAI_API_KEY or GEMINI_API_KEY env var)')
+  .option('-m, --model <model>', 'AI model to use (default: gpt-3.5-turbo for OpenAI, llama3.2 for Ollama, haiku for Claude Code, gemini-2.5-flash-lite for Gemini)')
   .option('--ollama-url <url>', 'Ollama server URL', 'http://localhost:11434')
   .option('-b, --branch <branch>', 'Branch to rewrite (defaults to current branch)')
   .option('-d, --dry-run', 'Show what would be changed without modifying repository')
@@ -176,9 +183,8 @@ program
 
       // Check for API key if using OpenAI
       const provider = options.provider || 'openai';
-      const apiKey = options.apiKey || process.env.OPENAI_API_KEY;
-
-      if (provider === 'openai' && !apiKey) {
+
+      if (provider === 'openai' && !options.apiKey && !process.env.OPENAI_API_KEY) {
         console.error(chalk.red('\n❌ Error: OpenAI API key is required!'));
         console.error(chalk.yellow('\nPlease provide it using one of these methods:'));
         console.error(chalk.cyan('  1. Set environment variable: export OPENAI_API_KEY="your-api-key"'));
@@ -187,6 +193,15 @@ program
         console.error(chalk.blue('\n💡 Tip: Use --provider ollama to use local models with Ollama instead'));
         process.exit(1);
       }
+
+      if (provider === 'gemini' && !options.apiKey && !process.env.GEMINI_API_KEY) {
+        console.error(chalk.red('\n❌ Error: Gemini API key is required!'));
+        console.error(chalk.yellow('\nPlease provide it using one of these methods:'));
+        console.error(chalk.cyan('  1. Set environment variable: export GEMINI_API_KEY="your-api-key"'));
+        console.error(chalk.cyan('  2. Pass as argument: git-rewrite-commits --provider gemini --api-key "your-api-key"'));
+        console.error(chalk.dim('\nGet your API key at: https://aistudio.google.com/app/apikey'));
+        process.exit(1);
+      }
 
       // Only show informational messages when NOT in quiet mode
       if (provider === 'ollama' && !options.quiet) {
@@ -199,9 +214,14 @@ program
         console.log(chalk.gray('   Make sure Claude Code is installed and authenticated: claude login'));
       }
 
+      if (provider === 'gemini' && !options.quiet) {
+        console.log(chalk.blue('ℹ️  Using Gemini provider'));
+        console.log(chalk.gray('   Make sure GEMINI_API_KEY is set or pass --api-key'));
+      }
+
       const rewriter = new GitCommitRewriter({
         provider: provider,
-        apiKey,
+        apiKey: options.apiKey || (provider === 'gemini' ? process.env.GEMINI_API_KEY : process.env.OPENAI_API_KEY),
         model: options.model,
         ollamaUrl: options.ollamaUrl,
         branch: options.branch,
@@ -280,10 +300,14 @@ ${chalk.bold('Examples:')}
   ${chalk.gray('# Use Ollama with local models')}
   $ git-rewrite-commits --provider ollama --model llama3.2
 
-  ${chalk.gray('# Use Claude Code CLI (no API key needed, uses Claude subscription)')}
+   ${chalk.gray('# Use Claude Code CLI (no API key needed, uses Claude subscription)')}
   $ git-rewrite-commits --provider claude-code
   $ git-rewrite-commits --provider claude-code --model opus
 
+  ${chalk.gray('# Use Gemini (gemini-2.5-flash-lite by default)')}
+  $ git-rewrite-commits --provider gemini
+  $ git-rewrite-commits --provider gemini --model gemini-2.5-flash-lite --api-key "your-key"
+
   ${chalk.gray('# Custom prompt for specific requirements')}
   $ git-rewrite-commits --prompt "generate humorous but professional messages"
 
@@ -292,6 +316,7 @@ ${chalk.bold('Examples:')}
 
 ${chalk.bold('Environment Variables:')}
   OPENAI_API_KEY    Your OpenAI API key (required when using OpenAI provider)
+  GEMINI_API_KEY    Your Gemini API key (required when using Gemini provider)
 
 ${chalk.bold('Important Notes:')}
   ${chalk.yellow('⚠️  This tool rewrites git history!')}

src/index.ts

@@ -7,7 +7,7 @@ import ora from 'ora';
 import { AIProvider, createProvider } from './providers/index.js';
 
 export interface RewriteOptions {
-  provider?: 'openai' | 'ollama' | 'claude-code';
+  provider?: 'openai' | 'ollama' | 'claude-code' | 'gemini';
   apiKey?: string;
   model?: string;
   ollamaUrl?: string;
@@ -41,6 +41,7 @@ export class GitCommitRewriter {
     const model = options.model || (
       provider === 'ollama' ? 'llama3.2' :
       provider === 'claude-code' ? 'haiku' :
+      provider === 'gemini' ? 'gemini-2.5-flash-lite' :
       'gpt-3.5-turbo'
     );
 
@@ -74,7 +75,7 @@ export class GitCommitRewriter {
 
   private execCommand(command: string): string {
     try {
-      return execSync(command, { encoding: 'utf-8', maxBuffer: 10 * 1024 * 1024 });
+      return execSync(command, { encoding: 'utf-8', maxBuffer: 10 * 1024 * 1024, stdio: ['pipe', 'pipe', 'pipe'] });
     } catch (error: any) {
       throw new Error(`Command failed: ${command}\n${error.message}`);
     }

src/providers/gemini.ts

@@ -0,0 +1,39 @@
+import { GoogleGenerativeAI } from '@google/generative-ai';
+import { AIProvider } from './types.js';
+
+export class GeminiProvider implements AIProvider {
+  private genAI: GoogleGenerativeAI;
+  private model: string;
+
+  constructor(apiKey: string, model: string = 'gemini-2.5-flash-lite') {
+    if (!apiKey) {
+      throw new Error('Gemini API key is required');
+    }
+    this.genAI = new GoogleGenerativeAI(apiKey);
+    this.model = model;
+  }
+
+  async generateCommitMessage(prompt: string, systemPrompt: string): Promise<string> {
+    const generativeModel = this.genAI.getGenerativeModel({
+      model: this.model,
+      systemInstruction: systemPrompt,
+      generationConfig: {
+        temperature: 0.3,
+        maxOutputTokens: 200,
+      },
+    });
+
+    const result = await generativeModel.generateContent(prompt);
+    const message = result.response.text().trim();
+
+    if (!message) {
+      throw new Error('No commit message generated');
+    }
+
+    return message;
+  }
+
+  getName(): string {
+    return `Gemini (${this.model})`;
+  }
+}

src/providers/index.ts

@@ -2,11 +2,13 @@ import { AIProvider, ProviderOptions } from './types.js';
 import { OpenAIProvider } from './openai.js';
 import { OllamaProvider } from './ollama.js';
 import { ClaudeCodeProvider } from './claude-code.js';
+import { GeminiProvider } from './gemini.js';
 
 export { AIProvider } from './types.js';
 export { OpenAIProvider } from './openai.js';
 export { OllamaProvider } from './ollama.js';
 export { ClaudeCodeProvider } from './claude-code.js';
+export { GeminiProvider } from './gemini.js';
 
 export function createProvider(options: ProviderOptions): AIProvider {
   const providerType = options.provider || 'openai';
@@ -15,6 +17,12 @@ export function createProvider(options: ProviderOptions): AIProvider {
     return new OllamaProvider(options.model || 'llama3.2', options.ollamaUrl);
   } else if (providerType === 'claude-code') {
     return new ClaudeCodeProvider(options.model || 'haiku');
+  } else if (providerType === 'gemini') {
+    const apiKey = options.apiKey || process.env.GEMINI_API_KEY;
+    if (!apiKey) {
+      throw new Error('Gemini API key is required. Set GEMINI_API_KEY environment variable or pass it as an option.');
+    }
+    return new GeminiProvider(apiKey, options.model || 'gemini-2.5-flash-lite');
   } else {
     const apiKey = options.apiKey || process.env.OPENAI_API_KEY;
     if (!apiKey) {

src/providers/types.ts

@@ -4,7 +4,7 @@ export interface AIProvider {
 }
 
 export interface ProviderOptions {
-  provider?: 'openai' | 'ollama' | 'claude-code';
+  provider?: 'openai' | 'ollama' | 'claude-code' | 'gemini';
   apiKey?: string;
   model?: string;
   ollamaUrl?: string;