code: private String addEvidenceFromVersionFile(Dependency dependency, EvidenceType type, File dependencyFile) {
          final File parentDir = dependencyFile.getParentFile();
          String version = null;
          int versionCount = 0;
          if (parentDir != null) {
              final File[] matchingFiles = parentDir.listFiles(new FilenameFilter() {
                  @Override
                  public boolean accept(File dir, String name) {
                      return name.contains(VERSION_FILE_NAME);
                  }
              });
              if (matchingFiles == null) {
                  return null;
              }
              for (File f : matchingFiles) {
                  try {
                      final List<String> lines = FileUtils.readLines(f, Charset.defaultCharset());
                      if (lines.size() == 1) { //TODO other checking?
                          final String value = lines.get(0).trim();
                          if (version == null || !version.equals(value)) {
                              version = value;
                              versionCount++;
                          }
  
                          dependency.addEvidence(type, GEMSPEC, "version", value, Confidence.HIGH);
                      }
                  } catch (IOException e) {
                      LOGGER.debug("Error reading gemspec", e);
                  }
              }
          }
          if (versionCount == 1) {
              return version;
          }
          return null;
      }
docs: Adds evidence from the version file.
  
  @param dependency the dependency being analyzed
  @param type the type of evidence to add
  @param dependencyFile the dependency being analyzed
  @return the version number added