title: Show all branches merged to Master between 2 dates - Git
body: <p>With git log I can use --since and --until to show data between 2 dates. 
  And with git branch -r I can extract all the remote branches.</p>
  
  <p>How would I show all branches merged to master between 2 dates? </p>
  
  <pre><code>git log --since "DEC 1 2019" --until "JAN 1 2020" --pretty=format:"%h %an %ad"
  </code></pre>
  
  <p>This returns all commits between 2 dates but I'd like to return the branch names between these 2 dates that were merged to master?</p>
  
  <p>Thanks in advance.</p>