title: Git clone verbose output?
body: <p>I have to clone a couple of big repos in my Dockerfile. It really can take an hour to clone a single repo and I want to see standard Git progress output to understand what's going on.</p>
  
  <p>However, when Git is started from the Dockerfile, I see no git clone output whatsoever. The only thing printed to console is:</p>
  
  <pre><code>Cloning into '/root/lib/opencv'...
  POST git-upload-pack (gzip 2052 to 1062 bytes)
  </code></pre>
  
  <p>and then just a silence. While, usually, I expect something like this:</p>
  
  <pre><code>Cloning into 'opencv'...
  POST git-upload-pack (gzip 2040 to 1052 bytes)
  remote: Counting objects: 158365, done.
  Receiving objects:   8% (12670/158365), 2.32 MiB | 255.00 KiB/s
  ... and so on ...
  </code></pre>
  
  <p>How to enable git verbose output in docker build? Maybe I have to start some interactive mode?</p>