code: private Double getPercentCoverageForDays(Iterable<Commit> commits, int days) {
      Set<String> dates = new HashSet<>();
      for (Commit commit : commits) {
        dates.add(Constants.DAY_FORMAT.format(new Date(commit.getScmCommitTimestamp())));
      }
      return (dates.size() / (double) days) * 100;
    }
docs: Calculate percentage of days with commits out of total days
  
  @param commits
  @param days
  @return percentage of days with commits