title: How to skip `(Y/n)` prompt when running firebase login
body: <p>I am trying to set up firebase CLI in my continuous integration (travis-ci, not that it really matters) and I inevitably have to login to firebase.</p>
  
  <pre class="lang-sh prettyprint-override"><code>$ firebase login --token FIREBASE_TOKEN --no-localhost
  ]0;Firebase CLIi  Firebase optionally collects CLI usage and error reporting information to help improve our products. Data is collected in accordance with Google's privacy policy (https://policies.google.com/privacy) and is not used to identify you.
  ? Allow Firebase to collect CLI usage and error reporting information? (Y/n) 
  </code></pre>
  
  <p>Since it's just travis-ci, there's no way for it to answer yes or no to that prompt, which hangs and kills the build.</p>
  
  <p>I did check <code>firebase login</code>'s <code>--help</code> and here's what I got:</p>
  
  <pre class="lang-sh prettyprint-override"><code>&gt; firebase login --help
  Usage: firebase login [options]
  
  log the CLI into Firebase
  
  Options:
    --no-localhost  copy and paste a code instead of starting a local server for authentication
    --reauth        force reauthentication even if already logged in
    -h, --help      output usage information
  </code></pre>
  
  <p>So there doesn't seem to be any kind of override flag like <code>-y</code> or anything.</p>
  
  <p>How am I supposed to log into firebase in my continuous build if there's no way to skip this prompt? Alternatively, how can I skip this prompt?</p>
  
  <p>I think it can't be complicated because support for "CI Systems" is outlined in <a href="https://firebase.google.com/docs/cli#cli-ci-systems" rel="nofollow noreferrer">Firebase's own docs</a>.</p>
  
  <p>Edit: Attempted with <code>login:ci</code></p>
  
  <pre class="lang-sh prettyprint-override"><code>$ firebase login:ci --token $FIREBASE_TOKEN
  ]0;Firebase CLI
  Visit this URL on this device to log in:
  https://accounts.google.com/o/oauth2/auth?client_id=...
  Waiting for authentication...
  </code></pre>