title: BFG remove multiple folders
body: <p>I found that BFG is much faster than the original git-filter-branch.</p>
  
  <p>We have multiple svn repo to move to even more git repositories, this implies some repository folder merges and splits.
  During the process I need to remove a set of root folders and I'd like to remove those to the whole history.</p>
  
  <p>I tried to use the BFG <strong>--delete-folders</strong> and it works fine for one single folder but I did not find a way to delete multiple folders. Is it even possible ? or shall I loop to call BFG as many times as I have folders to remove ?</p>
  
  <p>Thanks for any help.</p>