fix(router): allow relative navigation from index pages

test/integration/client-navigation/pages/nav/relative/index.js

@@ -0,0 +1,10 @@
+import Link from 'next/link'
+
+export default function Relative() {
+  return (
+    <div id="relative">
+      On relative index
+      <Link href="./relative-1">To relative 1</Link>
+    </div>
+  )
+}

test/integration/client-navigation/pages/nav/relative/relative-1.js

@@ -0,0 +1,12 @@
+import Link from 'next/link'
+
+export default function Relative1() {
+  return (
+    <div id="relative-1">
+      On relative 1
+      <Link href="./relative-2">
+        <a>To relative 2</a>
+      </Link>
+    </div>
+  )
+}

test/integration/client-navigation/pages/nav/relative/relative-2.js

@@ -0,0 +1,18 @@
+import { useRouter } from 'next/router'
+
+export default function Relative2() {
+  const router = useRouter()
+  return (
+    <div id="relative-2">
+      On relative 2
+      <button
+        onClick={(e) => {
+          e.preventDefault()
+          router.push('.')
+        }}
+      >
+        To relative index
+      </button>
+    </div>
+  )
+}

test/integration/client-navigation/test/index.test.js

@@ -1564,6 +1564,28 @@ describe('Client Navigation', () => {
     expect(value).toBe(false)
   })
 
+  it('should navigate to paths relative to the current page', async () => {
+    const browser = await webdriver(context.appPort, '/nav/relative')
+    await browser.waitForElementByCss('body', 500)
+    let page
+
+    await browser.elementByCss('a').click()
+    page = await browser.elementByCss('body').text()
+    expect(page).toMatch('On relative 1')
+    await browser.elementByCss('a').click()
+
+    browser.waitForElementByCss('#relative-2', 500)
+    page = await browser.elementByCss('body').text()
+    expect(page).toMatch(/On relative 2/)
+
+    await browser.elementByCss('button').click()
+    browser.waitForElementByCss('#relative', 500)
+    page = await browser.elementByCss('body').text()
+    expect(page).toMatch(/On relative index/)
+
+    await browser.close()
+  })
+
   renderingSuite(
     (p, q) => renderViaHTTP(context.appPort, p, q),
     (p, q) => fetchViaHTTP(context.appPort, p, q),