[clangd] Don't show all refs results if -name is ambiguous in dexp.

clangd/index/dex/dexp/Dexp.cpp

if (ID.getNumOccurrences()) {
       auto SID = SymbolID::fromStr(ID);
       if (!SID) {
         outs() << toString(SID.takeError()) << "\n";
         return;
       }
       IDs.push_back(*SID);
     } else {
       IDs = getSymbolIDsFromIndex(Name, Index);
+      if (IDs.size() > 1) {
+        outs() << formatv("The name {0} is ambiguous, found {1} different "
+                          "symbols. Please use id flag to disambiguate.\n",
+                          Name, IDs.size());
+        return;
+      }
     }
     RefsRequest RefRequest;
     RefRequest.IDs.insert(IDs.begin(), IDs.end());
     Regex RegexFilter(Filter);
     Index->refs(RefRequest, [&RegexFilter](const Ref &R) {
       auto U = URI::parse(R.Location.FileURI);
       if (!U) {
         outs() << U.takeError();