code: public @CheckForNull Plugin getPlugin(String artifactId, @CheckForNull VersionNumber minVersion) {
          if (minVersion == null) {
              return getPlugin(artifactId);
          }
          for (UpdateSite s : sites) {
              Plugin p = s.getPlugin(artifactId);
              if (p!=null) {
                  if (minVersion.isNewerThan(new VersionNumber(p.version))) continue;
                  return p;
              }
          }
          return null;
      }
docs: Gets the plugin with the given name from the first {@link UpdateSite} to contain it.
  @return Discovered {@link Plugin}. {@code null} if it cannot be found