docs: function step1 ( srcs ) {
  				var map = Object.create ( null );
  				function next ( source, parts, map ) {
  					var part = parts.shift ();
  					if ( !parts.length ) {
  						map [ part ] = source;
  					} else {
  						map [ part ] = map [ part ] || Object.create ( null );
  						next ( source, parts, map [ part ]);
  					}
  				}
  				srcs.forEach ( function ( source ) {
  					next ( source, source.split ( "/" ), map );
  				});
  				return map;
  			}