title: Whether the `git log` the first commit is the branch's present commit?
body: <p>Whether the <code>git log</code> the first commit is the branch's present commit?</p>
  
  <p>I use <code>git log</code> list the commits:</p>
  
  <pre><code>$ git log
  
  commit 75a80c128ea8b28f946b1bd55afa65cc1802bee5
  Author: lio &lt;lio@126.com&gt;
  Date:   Wed May 9 22:00:35 2018 +0800
  
      2018-05-09-11
  
  commit a57089b64890e5602a39dc33dc1f07d620d8a870
  Merge: c57feb6 9116e2b
  Author: lio &lt;lio@126.com&gt;
  Date:   Wed May 9 21:52:13 2018 +0800
  
      Merge branch 'master' of 103.200.32.76:/home/ldl/repo/Qiyun02
  
  commit c57feb677a170d786756c97cb71f6225ba9e6774
  Author: lio &lt;lio@126.com&gt;
  Date:   Wed May 9 21:48:50 2018 +0800
  
      2018-05-09-10
  
  commit 9116e2b15605590a2db437bee2f7b83f3f9271ff
  Author: root &lt;root@www.lio.xyz&gt;
  Date:   Wed May 9 13:47:28 2018 +0800
  ...
  </code></pre>
  
  <p>whether the first commit <code>75a80c128ea8b28f946b1bd55afa65cc1802bee5</code> is the branch's current commit? </p>