Make it possible to unset the default user-agent header (#496)

index.js

@@ -546,6 +546,10 @@ function normalizeArguments(url, opts) {
 	};
 
 	const headers = lowercaseKeys(opts.headers);
+	if (!Object.keys(headers).includes('user-agent')) {
+		headers['user-agent'] = `${pkg.name}/${pkg.version} (https://github.com/sindresorhus/got)`;
+	}
+
 	for (const [key, value] of Object.entries(headers)) {
 		if (is.nullOrUndefined(value)) {
 			delete headers[key];

readme.md

@@ -105,6 +105,15 @@ Type: `Object`
 
 Any of the [`https.request`](https://nodejs.org/api/https.html#https_https_request_options_callback) options.
 
+###### headers
+
+Type: `Object`<br>
+Default: `{}`
+
+Request headers.
+
+Existing headers will be overwritten. Headers set to `null` or `undefined` will be omitted.
+
 ###### stream
 
 Type: `boolean`<br>
@@ -635,7 +644,7 @@ const createTestServer = require('create-test-server');
 
 ### User Agent
 
-It's a good idea to set the `'user-agent'` header so the provider can more easily see how their resource is used. By default, it's the URL to this repo.
+It's a good idea to set the `'user-agent'` header so the provider can more easily see how their resource is used. By default, it's the URL to this repo. You can omit this header by setting it to `null` or `undefined`.
 
 ```js
 const got = require('got');
@@ -646,6 +655,12 @@ got('sindresorhus.com', {
 		'user-agent': `my-module/${pkg.version} (https://github.com/username/my-module)`
 	}
 });
+
+got('sindresorhus.com', {
+	headers: {
+		'user-agent': null
+	}
+});
 ```
 
 ### 304 Responses

test/headers.js

@@ -128,21 +128,21 @@ test('stream as options.body sets content-length', async t => {
 test('remove null value headers', async t => {
 	const {body} = await got(s.url, {
 		headers: {
-			unicorns: null
+			'user-agent': null
 		}
 	});
 	const headers = JSON.parse(body);
-	t.false(Reflect.has(headers, 'unicorns'));
+	t.false(Reflect.has(headers, 'user-agent'));
 });
 
 test('remove undefined value headers', async t => {
 	const {body} = await got(s.url, {
 		headers: {
-			unicorns: undefined
+			'user-agent': undefined
 		}
 	});
 	const headers = JSON.parse(body);
-	t.false(Reflect.has(headers, 'unicorns'));
+	t.false(Reflect.has(headers, 'user-agent'));
 });
 
 test.after('cleanup', async () => {