title: Specify Flutter version during upgrade
body: <p>I work on a Flutter application on two different PC's and would like the Flutter version to be the same for both. I am on the <code>dev</code> channel and when I do a <code>flutter upgrade</code> it ugrades to the latest version in that channel.</p>
  
  <p>Two days ago I did a <code>flutter upgrade</code> on one PC and it went to version <code>1.2.2</code>. Today on my other PC I did a <code>flutter upgrade 1.2.2</code> but it went to version <code>1.3.2</code> instead.</p>
  
  <p>Is there a way for me to specify the flutter version when upgrading?</p>