function(systemId, target, cb) {
    listRevisions(systemId, function(err, revs) {
      if (err) { return cb(err); }
      getRevision(systemId, revs[0].id, target, cb);
    });
  }
function(systemId, target, cb) {
    listRevisions(systemId, function(err, revs) {
      if (err) { return cb(err); }
      getRevision(systemId, revs[0].id, target, cb);
    });
  }
function ( systemId , target , cb ) { listRevisions ( systemId , function ( err , revs ) { if ( err ) { return cb ( err ) ; } getRevision ( systemId , revs [ 0 ] . id , target , cb ) ; } ) ; }
get the head revision for a system
get the head revision for a system