[clang-tools-extra] [clangd] Unify IndexAction callbacks into one (PR #178132)

[Nathan Ridge via cfe-commits]

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@@ -161,9 +157,8 @@ class IndexAction : public ASTFrontendAction {
   std::unique_ptr<ASTConsumer>
   CreateASTConsumer(CompilerInstance &CI, llvm::StringRef InFile) override {
     PI->record(CI.getPreprocessor());
-    if (IncludeGraphCallback != nullptr)
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HighCommander4 wrote:

This is one part of the change I'm unsure about. `clangd-indexer` doesn't currently pass an `IncludeGraphCallback`, and so saves a bit of work here -- but that may be an oversight / missing feature in `clangd-indexer`?

https://github.com/llvm/llvm-project/pull/178132