code: function singleEntrySourceMap(entryItem, entryData, sourceMap, callback) { // eslint-disable-line
    if (typeof entryItem !== 'string') { return callback(null, sourceMap); }
  
    // get input sources for this entry
    getInputSources(entryItem, (inputSourceError, inputSourceMap) => { // eslint-disable-line
      if (inputSourceError) { return callback(inputSourceError, null); }
  
      // get source data
      const sourceData = deepAssign({}, sourceMap, inputSourceMap);
  
      // get next entry item
      const nextEntryItem = entryData[entryData.indexOf(entryItem) + 1];
  
      // recursively go through tree
      singleEntrySourceMap(nextEntryItem, entryData, sourceData, callback);
    });
  }
docs: Get source map for a single config object entry path.
  
  @method singleEntrySourceMap
  @param {String} entryItem the entry item string, generally a file or dir path
  @param {Array} entryData the entry data
  @param {Object} sourceMap the source map
  @callback {Function} callback the callback