title: git confusing graph. `master` branch seems to have two lines?
body: <p>On running <code>git log</code> i am seeing strange graph. I will explain it further.
  Below is the output for git log with graph.</p>
  
  <pre><code>$ git log --graph  --oneline
  *   df1834d (HEAD -&gt; master, tag: r-0.1, origin/master) Merge branch 'master' of https://github.com/samshers/graphql-hibernate
  |\
  | * d56a675 fixed country null issue
  * | ee9bb70 fixed country null issue
  |/
  * 2617f2a hibernate cascade error issue. country field in state table set to null
  </code></pre>
  
  <p>As you an see master has two separate branches in itself. To confirm this further, i ran </p>
  
  <pre><code>$ git branch --contains ee9bb706c8fcc329fac4acf69ad6b684f1069170
    joincolumn_issue
    ls
    mappedBy
  * master
  </code></pre>
  
  <p>And then</p>
  
  <pre><code>$ git branch --contains d56a6751771b1f62d9ceb0bcce9a2391c004ee44
    joincolumn_issue
    ls
    mappedBy
  * master
  </code></pre>
  
  <p><strong>So clearly these two commits are present on master - so then why are there two graphs.</strong> 
  How can i know if <strong>changes</strong> both the commits are present on master. Or if only <strong>changes</strong> from one of them is actually present on the master, which one of the two?     </p>
  
  <p><strong>Edit - following responses from RY and Mark</strong>
  <a href="https://i.stack.imgur.com/nYa1M.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/nYa1M.png" alt="adding the graph screenshot"></a>   ( if color codes add any further meaning, please hint on that as well.)<br>
  So, am further trying to understand why a commit (Y) is not based on previous commit (X) ( if X was committed before Y). 
  The git log shows that both <code>d56a675</code> and <code>ee9bb70</code>  where committed at the same time. </p>
  
  <pre><code>commit ee9bb706c8fcc329fac4acf69ad6b684f1069170
  Author: itsvamshers &lt;itsvamshers@gmail.com&gt;
  Date:   Mon Sep 9 17:24:01 2019 +0530
  
      fixed country null issue
  
  commit d56a6751771b1f62d9ceb0bcce9a2391c004ee44
  Author: itsvamshers &lt;itsvamshers@gmail.com&gt;
  Date:   Mon Sep 9 17:24:01 2019 +0530
  
      fixed country null issue
  </code></pre>
  
  <p>But, on digging further the little difference can be seen..</p>
  
  <pre><code>$ git show -s --format="%ct" d56a6751771b1f62d9ceb0bcce9a2391c004ee44
  1568030041
  </code></pre>
  
  <p>and </p>
  
  <pre><code>$  git show -s --format="%ct"  ee9bb706c8fcc329fac4acf69ad6b684f1069170
  1568031643
  </code></pre>
  
  <p>and this info should be enough for git to put the commits in right order. But if it is not, then I guess it is smarter and doing it for reason, just trying to understand the reason and the cause.</p>