Failed to update brew: "The following untracked working tree files would be overwritten by merge" I'm trying to update brew but I get this error message: 


  error: The following untracked working tree files would be overwritten by merge:
      Library/Formula/curlpp.rb
  Please move or remove them before you can merge.




The directory /Library/Formula doesn't even exist. What should I do?
Be aware of what messages said. 


  Please move or remove them before you can merge.


So, let's move it.

mv /usr/local/Library/Formula/curlpp.rb /usr/local/Library/Formula/curlpp.rb.old


Then try again:

brew upgrade