src/artifact_collector.js
function followEntryRefs( key, callback ) {
   return function( entry ) {
      const refs = entry[ key ] || [];
      return Promise.all( refs.map( callback ) ).then( flatten );
   };
}
function followEntryRefs( key, callback ) {
   return function( entry ) {
      const refs = entry[ key ] || [];
      return Promise.all( refs.map( callback ) ).then( flatten );
   };
}
function followEntryRefs ( key , callback ) { return function ( entry ) { const refs = entry [ key ] || [ ] ; return Promise . all ( refs . map ( callback ) ) . then ( flatten ) ; } ; }
Create a function that expects an artifact entry as a parameter and follows the given key of it with
a given function.

@private
@param {String} key the key to follow
@param {Function} callback the function to call for each ref listed in the key
@return {Function} a function returning a promise for a list of entries returned by callback
Create a function that expects an artifact entry as a parameter and follows the given key of it with a given function .