[clangd] Log version, cwd, args, and transport on startup. NFC

[hokein]

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

436

this variable is not used.

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

int main(int argc, char *argv[]) {
   if (Tracer)
     TracingSession.emplace(*Tracer);
 
   // Use buffered stream to stderr (we still flush each log message). Unbuffered
   // stream can cause significant (non-deterministic) latency for the logger.
   llvm::errs().SetBuffered();
   StreamLogger Logger(llvm::errs(), LogLevel);
   LoggingSession LoggingSession(Logger);
+  // Write some initial logs before we start doing any real work.
+  log("{0}", clang::getClangToolFullVersion("clangd"));
+  {
+    SmallString<128> CWD;
+    if (auto Err = llvm::sys::fs::current_path(CWD))
+      log("Working directory unknown: {0}", Err.message());
+    else
+      log("Working directory: {0}", CWD);
+  }
+  {
+    std::string LoggableArgs;
+    for (int I = 0; I < argc; ++I)
+      log("argv[{0}]: {1}", I, argv[I]);
+  }
 
   // If --compile-commands-dir arg was invoked, check value and override default
   // path.
   llvm::Optional<Path> CompileCommandsDirPath;
   if (!CompileCommandsDir.empty()) {
     if (llvm::sys::fs::exists(CompileCommandsDir)) {
       // We support passing both relative and absolute paths to the
       // --compile-commands-dir argument, but we assume the path is absolute in
int main(int argc, char *argv[]) {
   RealFileSystemProvider FSProvider;
   // Initialize and run ClangdLSPServer.
   // Change stdin to binary to not lose \r\n on windows.
   llvm::sys::ChangeStdinToBinary();
 
   std::unique_ptr<Transport> TransportLayer;
   if (getenv("CLANGD_AS_XPC_SERVICE")) {
 #if CLANGD_BUILD_XPC
+    log("Starting LSP over XPC service");
     TransportLayer = newXPCTransport();
 #else
     llvm::errs() << "This clangd binary wasn't built with XPC support.\n";
     return (int)ErrorResultCode::CantRunAsXPCService;
 #endif
   } else {
+    log("Starting LSP over stdin/stdout");
     TransportLayer = newJSONTransport(
         stdin, llvm::outs(),
         InputMirrorStream ? InputMirrorStream.getPointer() : nullptr,
         PrettyPrint, InputStyle);
   }
 
   // Create an empty clang-tidy option.
   std::mutex ClangTidyOptMu;