public static boolean isUserAgentEnabled() {
    return Strings.isNullOrEmpty(System.getProperty(DISABLE_USER_AGENT));
  }
Gets whether or not to enable the User-Agent header. This is defined by the {@code
_JIB_DISABLE_USER_AGENT} system property.

@return {@code true} if the User-Agent header is enabled, {@code false} if not
jib-core/src/main/java/com/google/cloud/tools/jib/global/JibSystemProperties.java