public void add(
     @NonNull SCM scm,
     @NonNull FilePath ws,
     @Nullable Run<?, ?> build,
     SCMRevisionState scmState) {
   revisionStates.put(scm.getKey(), scmState);
 }
 public SCMRevisionState get(
     @NonNull SCM scm, @NonNull FilePath ws, @Nullable AbstractBuild<?, ?> build) {
   SCMRevisionState state = revisionStates.get(scm.getKey());
   if (state == null) {
     // backward compatibility with 0.2
     state = revisionStates.get(keyFor(scm, ws, build));
   }
   // for backward compatibility with version 0.1, try to get the state using the class name as
   // well
   if (state == null) state = revisionStates.get(scm.getClass().getName());
   return state;
 }