title: Git - how to find first commit of specific branch
body: <p>In following example tree:</p>
  
  <pre><code>A-B-C-D-E (master branch)
      \
       F-G-H (xxx branch)
  </code></pre>
  
  <p>I'm looking for F - the first commit in xxx branch. I think that it is possible with:</p>
  
  <pre><code>git log xxx --not master
  </code></pre>
  
  <p>and the last listed commit should be F. Is it correct solution or maybe there are some disadvantages of it? </p>
  
  <p>I know that there were similar questions on stackoverflow, but nobody proposed such solution, and I'm not sure if I do it right.</p>