title: react router - don't match multiple paths (v4)
body: <p>I have the following react-router configuration</p>
  
  <pre><code>import React from 'react'
  import { BrowserRouter, Route } from 'react-router-dom'
  
  &lt;BrowserRouter&gt;
    &lt;Route exact path='/sign-in' component={SignIn} /&gt;
    &lt;Route exact path='/:username' component={Profile} /&gt;
  &lt;/BrowserRouter&gt;
  </code></pre>
  
  <p>When on a profile page like <code>/dylan</code> the Profile component matches and :username param is "dylan" like I would expect.</p>
  
  <p>When navigating to the <code>/sign-in</code> route, the  component gets rendered and the  component get rendered too (with <code>sign-in</code> as the username)</p>
  
  <p>What is the idiomatic solution with react-router v4 to prevent routes from matching multiple components?</p>
  
  <p>versions:</p>
  
  <ul>
  <li>react-router-dom 4.1.2</li>
  </ul>