code: function (storeOrEditor, from, to) {
      debug('Performing inMemoryCopy from ' + from + ' to ' + to + '.');
      var fromLen = from.length;
      this.processInMemoryStore(storeOrEditor, (file, store) => {
        var idx = file.path.indexOf(from);
        if (idx === 0 && file.contents !== null && file.state !== 'deleted') {
          var absTo = path.join(to, file.path.substr(fromLen));
          // exact match so we are copying a single file and not a folder
          if (fromLen === file.path.length) {
            absTo = path.join(to, path.basename(file.path));
          }
          debug('CREATING COPY IN-MEMORY: ' + absTo);
          var newFile = store.get(absTo);
          newFile.contents = file.contents;
          newFile.state = 'modified';
          store.add(newFile);
        }
      });
    }
docs: Given the path for a virtual file or folder and a destination path perform a copy
  completely within mem-fs.
  
  @param {!Store|!EditionInterface} storeOrEditor
  @param {string} from - file path or folder path
  @param {string} to - folder path