diff --git a/src/cli.ts b/src/cli.ts
index 13dffde..2bd66b5 100644
--- a/src/cli.ts
+++ b/src/cli.ts
@@ -3,82 +3,54 @@ import chalk from 'chalk';
 import inquirer from 'inquirer';
 import {
 	getConfig,
+	assertGitRepo,
+	getStagedDiff,
 	generateCommitMessage,
 } from './utils.js';
 
 (async () => {
+	console.log(chalk.white('▲ ') + chalk.green('Welcome to AICommits!'));
+
+	await assertGitRepo();
+
+	const staged = await getStagedDiff();
+	if (!staged) {
+		throw new Error('No staged changes found. Make sure to stage your changes with `git add`.');
+	}
+
 	const config = await getConfig();
 	const OPENAI_KEY = process.env.OPENAI_KEY ?? process.env.OPENAI_API_KEY ?? config.OPENAI_KEY;
 
-	console.log(chalk.white('▲ ') + chalk.green('Welcome to AICommits!'));
-
 	if (!OPENAI_KEY) {
-		console.error(
-			`${chalk.white('▲ ')
-         }Please save your OpenAI API key as an env variable by doing 'export OPENAI_KEY=YOUR_API_KEY'`,
-		);
-		process.exit(1);
+		throw new Error('Please set your OpenAI API key in ~/.aicommits');
 	}
-	try {
-		await execa('git', ['rev-parse', '--is-inside-work-tree']);
-	} catch {
-		console.error(`${chalk.white('▲ ')}This is not a git repository`);
-		process.exit(1);
-	}
-
-	const { stdout: diff } = await execa(
-		'git',
-		['diff', '--cached', '.', ':(exclude)package-lock.json', ':(exclude)yarn.lock', ':(exclude)pnpm-lock.yaml'],
-	);
-
-	if (!diff) {
-		console.log(
-			`${chalk.white('▲ ')
-         }No staged changes found. Make sure there are changes and run \`git add .\``,
-		);
-		process.exit(1);
-	}
-
-	// Accounting for GPT-3's input req of 4k tokens (approx 8k chars)
-	if (diff.length > 8000) {
-		console.log(
-			`${chalk.white('▲ ')}The diff is too large to write a commit message.`,
-		);
-		process.exit(1);
-	}
-
-	const prompt = `I want you to act like a git commit message writer. I will input a git diff and your job is to convert it into a useful commit message. Do not preface the commit with anything, use the present tense, return a complete sentence, and do not repeat yourself: ${diff}`;
 
 	console.log(
 		chalk.white('▲ ') + chalk.gray('Generating your AI commit message...\n'),
 	);
+	const aiCommitMessage = await generateCommitMessage(OPENAI_KEY, staged.diff);
+	console.log(
+		`${chalk.white('▲')} ${chalk.bold('Commit message:')} ${aiCommitMessage}\n`,
+	);
 
-	try {
-		const aiCommitMessage = await generateCommitMessage(OPENAI_KEY, prompt);
-		console.log(
-			`${chalk.white('▲ ') + chalk.bold('Commit message: ') + aiCommitMessage
-		}\n`,
-		);
+	const confirmationMessage = await inquirer.prompt([
+		{
+			name: 'useCommitMessage',
+			message: 'Would you like to use this commit message? (Y / n)',
+			choices: ['Y', 'y', 'n'],
+			default: 'y',
+		},
+	]);
 
-		const confirmationMessage = await inquirer.prompt([
-			{
-				name: 'useCommitMessage',
-				message: 'Would you like to use this commit message? (Y / n)',
-				choices: ['Y', 'y', 'n'],
-				default: 'y',
-			},
-		]);
-
-		if (confirmationMessage.useCommitMessage === 'n') {
-			console.log(`${chalk.white('▲ ')}Commit message has not been commited.`);
-			process.exit(1);
-		}
-
-		await execa('git', ['commit', '-m', aiCommitMessage], {
-			stdio: 'inherit',
-		});
-	} catch (error) {
-		console.error(chalk.white('▲ ') + chalk.red((error as any).message));
-		process.exit(1);
+	if (confirmationMessage.useCommitMessage === 'n') {
+		console.log(`${chalk.white('▲ ')}Commit message has not been commited.`);
+		return;
 	}
-})();
+
+	await execa('git', ['commit', '-m', aiCommitMessage], {
+		stdio: 'inherit',
+	});
+})().catch((error) => {
+	console.error(`${chalk.white('▲')} ${error.message}`);
+	process.exit(1);
+});
diff --git a/src/utils.ts b/src/utils.ts
index 74b8d53..e9f21ab 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -2,6 +2,7 @@ import fs from 'fs/promises';
 import path from 'path';
 import os from 'os';
 import ini from 'ini';
+import { execa } from 'execa';
 import { Configuration, OpenAIApi } from 'openai';
 
 const fileExists = (filePath: string) => fs.access(filePath).then(() => true, () => false);
@@ -21,10 +22,27 @@ export const getConfig = async (): Promise<ConfigType> => {
 	return ini.parse(configString);
 };
 
+export const assertGitRepo = async () => {
+	const { stdout } = await execa('git', ['rev-parse', '--is-inside-work-tree'], { reject: false });
+
+	if (stdout !== 'true') {
+		throw new Error('The current directory must be a Git repository!');
+	}
+};
+
+const promptTemplate = 'I want you to act like a git commit message writer. I will input a git diff and your job is to convert it into a useful commit message. Do not preface the commit with anything, use the present tense, return a complete sentence, and do not repeat yourself:';
+
 export const generateCommitMessage = async (
 	apiKey: string,
-	prompt: string,
+	diff: string,
 ) => {
+	const prompt = `${promptTemplate}\n${diff}`;
+
+	// Accounting for GPT-3's input req of 4k tokens (approx 8k chars)
+	if (prompt.length > 8000) {
+		throw new Error('The diff is too large for the OpenAI API');
+	}
+
 	const openai = new OpenAIApi(new Configuration({ apiKey }));
 	try {
 		const completion = await openai.createCompletion({
@@ -46,3 +64,31 @@ export const generateCommitMessage = async (
 		throw errorAsAny;
 	}
 };
+
+const excludeFromDiff = [
+	'package-lock.json',
+	'yarn.lock',
+	'pnpm-lock.yaml',
+].map(file => `:(exclude)${file}`);
+
+export const getStagedDiff = async () => {
+	const diffCached = ['diff', '--cached'];
+	const { stdout: files } = await execa(
+		'git',
+		[...diffCached, '--name-only', ...excludeFromDiff],
+	);
+
+	if (!files) {
+		return;
+	}
+
+	const { stdout: diff } = await execa(
+		'git',
+		[...diffCached, ...excludeFromDiff],
+	);
+
+	return {
+		files: files.split('\n'),
+		diff,
+	};
+};