code: func mergeBuilds(a, b []*buildbot.Build) []*buildbot.Build {
  	ret := make([]*buildbot.Build, len(a), len(a)+len(b))
  	copy(ret, a)
  
  	// add builds from b that have unique build numbers.
  	aNumbers := make(map[int]struct{}, len(a))
  	for _, build := range a {
  		aNumbers[build.Number] = struct{}{}
  	}
  	for _, build := range b {
  		if _, ok := aNumbers[build.Number]; !ok {
  			ret = append(ret, build)
  		}
  	}
  	sort.Slice(ret, func(i, j int) bool {
  		return ret[i].Number > ret[j].Number
  	})
  	return ret
  }
docs: // mergeBuilds merges builds from a and b to one slice.
  // The returned builds are ordered by build numbers, descending.
  //
  // If a build number is present in both a and b, b's build is ignored.