title: What does git push -u mean?
body: <p>I have two different versions of git.
  In the 1.6.2 version, <code>git push</code> does not have the <code>-u</code> option. It only appears in the 1.7.x version.</p>
  
  <p>From the docs, the <code>-u</code> is related to the variable</p>
  
  <pre><code>branch.&lt;name&gt;.merge
  </code></pre>
  
  <p>in <code>git config</code>. This variable is described below:</p>
  
  <pre><code>Defines, together with branch.&lt;name&gt;.remote, the upstream branch 
  for the given branch. It tells git fetch/git pull which branch to merge.
  </code></pre>
  
  <p>What is an upstream branch ?</p>