[clangd] Update the out-of-date yaml-symbol-file flag in clangd.

[hokein]

Summary

The flag is stale due to the recent changes of clangd indexer, this
patch rename it to "index-file".

[sammccall]

Hmm, I wonder if we should remove "experimental" text and the hidden bit. Or wait to see if we want to move to automatic index entirely?
May want to mention "must have been created by a compatible clangd-indexer".

[hokein]

address comment.

[hokein]

In D52976#1257614, @sammccall wrote:

Hmm, I wonder if we should remove "experimental" text and the hidden bit. Or wait to see if we want to move to automatic index entirely?

Our plan seems unclear at the moment, so I would suggest not doing it now until we sort them out.

May want to mention "must have been created by a compatible clangd-indexer".

Done.

clang-tools-extra/trunk/clangd/tool/ClangdMain.cpp

 
 static llvm::cl::opt<bool> HeaderInsertionDecorators(
     "header-insertion-decorators",
     llvm::cl::desc("Prepend a circular dot or space before the completion "
                    "label, depending on whether "
                    "an include line will be inserted or not."),
     llvm::cl::init(true));
 
-static llvm::cl::opt<Path> YamlSymbolFile(
-    "yaml-symbol-file",
+static llvm::cl::opt<Path> IndexFile(
+    "index-file",
     llvm::cl::desc(
-        "YAML-format global symbol file to build the static index. Clangd will "
-        "use the static index for global code completion.\n"
+        "Index file to build the static index. The file must have been created "
+        "by a compatible clangd-index.\n"
         "WARNING: This option is experimental only, and will be removed "
         "eventually. Don't rely on it."),
     llvm::cl::init(""), llvm::cl::Hidden);
 
 enum CompileArgsFrom { LSPCompileArgs, FilesystemCompileArgs };
 static llvm::cl::opt<CompileArgsFrom> CompileArgsFrom(
     "compile_args_from", llvm::cl::desc("The source of compile commands"),
     llvm::cl::values(clEnumValN(LSPCompileArgs, "lsp",
case PCHStorageFlag::Disk:
     Opts.StorePreamblesInMemory = false;
     break;
   }
   if (!ResourceDir.empty())
     Opts.ResourceDir = ResourceDir;
   Opts.BuildDynamicSymbolIndex = EnableIndex;
   std::unique_ptr<SymbolIndex> StaticIdx;
   std::future<void> AsyncIndexLoad; // Block exit while loading the index.
-  if (EnableIndex && !YamlSymbolFile.empty()) {
+  if (EnableIndex && !IndexFile.empty()) {
     // Load the index asynchronously. Meanwhile SwapIndex returns no results.
     SwapIndex *Placeholder;
     StaticIdx.reset(Placeholder = new SwapIndex(llvm::make_unique<MemIndex>()));
     AsyncIndexLoad = runAsync<void>([Placeholder, &Opts] {
-      if (auto Idx = loadIndex(YamlSymbolFile, Opts.URISchemes, UseDex))
+      if (auto Idx = loadIndex(IndexFile, Opts.URISchemes, UseDex))
         Placeholder->reset(std::move(Idx));
     });
     if (RunSynchronously)
       AsyncIndexLoad.wait();
   }
   Opts.StaticIndex = StaticIdx.get();
   Opts.AsyncThreadsCount = WorkerThreadsCount;