svoid thinAProgramsBackups(S progID, bool doIt) {
  File dir = programDir(progID);
  thinAProgramsBackups(dir, doIt);
}

svoid thinAProgramsBackups(File dir, bool doIt) {
  new L<File> files;
  new Map<File, Double> ageMap;
  
  // minutes (last group) are optional
  java.util.regex.Pattern pat = regexp("^(.*)\\.backup(20\\d\\d)(\\d\\d)(\\d\\d)-(\\d\\d)(\\d*)$");
  print("Processing backups in " + dir);
  
  for (File f : listFilesNotDirs(dir, newFile(dir, "backups"))) {
    S s = f.getName();
    java.util.regex.Matcher matcher = pat.matcher(s);
    continue unless matcher.find();
    S originalName = matcher.group(1);
    continue unless eq(originalName, "concepts.structure.gz");
    //print("Found backup: " + sfu(matcherGroups(matcher)));
    int year = matcherInt(matcher, 2);
    int month = matcherInt(matcher, 3);
    int day = matcherInt(matcher, 4);
    int hour = matcherInt(matcher, 5);
    int minute = matcherInt(matcher, 6);
    long time = timestampFromYMDHM(year, month, day, hour, minute);
    double age = ((now()-time)/1000.0/60/60/24;
    //print("Age: " + age + " days");
    ageMap.put(f, age);
    files.add(f);
  }
  
  int numDeleted = 0;
  sortByMap_inPlace(files, ageMap);
  double lastAge = -1;
  for (File f : files) {
    double age = ageMap.get(f);
    if (!thinAProgramsBackups_shouldKeep(age, lastAge)) {
      //print("Deleting: " + f);
      ++numDeleted;
      if (doIt) {
        print("Deleting: " + f);
        f.delete();
      }
    } else {
      //print("Keeping: " + f);
      lastAge = age;
    }
  }
  if (numDeleted != 0)
    print((doIt ? "Deleted: " : "Would delete: ") + n(numDeleted, "file"));
}

// age = age in days
sbool thinAProgramsBackups_shouldKeep(double age, double lastAge) {
  ret defaultAgeBasedBackupRetentionStrategy_shouldKeep(age, lastAge);
}