code: protected void doGlobalVersioning(StaplerRequest req) {
          if (req.getParameter("releaseVersion") != null) {
              releaseVersion = req.getParameter("releaseVersion");
          }
          if (req.getParameter("nextVersion") != null) {
              nextVersion = req.getParameter("nextVersion");
          }
      }
docs: Execute the {@link VERSIONING#GLOBAL} strategy of the versioning mechanism, which assigns all modules the same
  version for the release and for the next development version.
  
  @param req The request that is coming from the form when staging.