title: Git merge finds conflict after reverting to common version between branches
body: <p>I have two branches called <code>test</code> and <code>prod-candidate</code>. These two branches have a common commit in their history, <code>a0e378cfe28</code>, which was originally in the test branch and was later merged into prod-candidate. After this commit, the two branches went different ways and had other commits associated to them.</p>
  
  <p>It is now time to merge test into prod-candidate again, so I was hoping that by reverting all the commits in the prod-candidate branch back to commit <code>a0e378cfe28</code> I would be able to do the merge without problems. I did the revert and by running <code>git diff</code> I was able to verify that the revert was successful because the prod-candidate branch has the exact same contents as commit <code>a0e378cfe28</code>.</p>
  
  <p>Unfortunately, after checking out prod-candidate and running <code>git merge test</code>, I am getting a conflict in the POM file and I can't understand why. The test branch has a POM with version <code>18.4.0-101</code>, and prod-candidate, which before the revert had version <code>18.3.0-204</code>, currently has version <code>18.3.0-101</code> (which is the same as commit <code>a0e378cfe28</code>).</p>
  
  <p>Why can't I merge the branches after reverting to a common base commit?</p>