title: How to get information where branch starts?
body: <p>As far as I know, commit object contains information only about parents, so if I have situation something like this:</p>
  
  <pre><code> *  branch-1
   |
   o
   |
   o  master
   |
   o 
  </code></pre>
  
  <p>which is some kind of equivalent of</p>
  
  <pre><code>   *  branch-1
     |
     o
    /
   o  master
   |
   o 
  </code></pre>
  
  <p>but what if my master will go forward?</p>
  
  <pre><code> o master
   |
   o *  branch-1
   | |
   o o
   |/
   o
   |
   o 
  </code></pre>
  
  <p>being on branch-1, <code>git log --graph --decorate</code> will show me only:</p>
  
  <pre><code> *  branch-1
   |
   o
   |
   o
   |
   o 
  </code></pre>
  
  <p>if I know from which branch I was started, I can call <code>git merge-base master branch-1</code>, but what if I don't know from which branch I was started?</p>
  
  <hr>
  
  <p>PS.
  I am still learning English, however sometimes I am making stupid mistakes. I am doing my best, writing questions and answers in English, however I would be very glad if you will edit my post in case of any mistakes. I promise, your effort will not be wasted.</p>