code: private boolean markAsObsolete(ContentReference ref) {
          if (obsoleteContents.containsKey(ref.getHexHash())) { //This content is already marked as obsolete
              if (obsoleteContents.get(ref.getHexHash()) + obsolescenceTimeout < System.currentTimeMillis()) {
                  DeploymentRepositoryLogger.ROOT_LOGGER.obsoleteContentCleaned(ref.getContentIdentifier());
                  removeContent(ref);
                  return true;
              }
          } else {
              obsoleteContents.put(ref.getHexHash(), System.currentTimeMillis()); //Mark content as obsolete
          }
          return false;
      }
docs: Mark content as obsolete. If content was already marked for obsolescenceTimeout ms then it is removed.
  
  @param ref the content refrence to be marked as obsolete.
  
  @return true if the content refrence is removed, fale otherwise.