code: public static void saveLastExecVersion() {
          if (Jenkins.VERSION.equals(Jenkins.UNCOMPUTED_VERSION)) {
              // This should never happen!! Only adding this check in case someone moves the call to this method to the wrong place.
              throw new IllegalStateException("Unexpected call to InstallUtil.saveLastExecVersion(). Jenkins.VERSION has not been initialized. Call computeVersion() first.");
          }
          saveLastExecVersion(Jenkins.VERSION);
      }
docs: Save the current Jenkins instance version as the last executed version.
  <p>
  This state information is required in order to determine whether or not the Jenkins instance
  is just restarting, or is being upgraded from an earlier version.