title: Find first commit specific to a branch
body: <p>Looking for commits A(master), C(0.1), K(0.1.1) and O(0.2). </p>
  
  <pre><code>A - B - D - F - G   &lt;- "master" branch (at G)
   \   \        
    \   C - E --M     &lt;- "0.1" branch (still at E)
     \       \
      \       K - L   &lt;- "0.1.1" branch (still at L)
       \
        O - P - F     &lt;- "0.2" branch (still at F)
  </code></pre>
  
  <p>How can detect this commits by scripts without user data about parent branch.
  In other words, how to determine the first commit (A, O, C, K), belongs to a particular branch, knowing only the name of this branch?</p>