[clang] [clang-tools-extra] [clang] Make deprecations of some `FileManager` APIs formal (PR #110014)

[Ben Langmuir via cfe-commits]

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@@ -199,7 +199,7 @@ int main(int argc, const char **argv) {
       for (auto I = Files.begin(), E = Files.end(); I != E; ++I) {
         OS << "  {\n";
         OS << "    \"FilePath\": \"" << *I << "\",\n";
-        const auto Entry = FileMgr.getFile(*I);
+        const auto Entry = FileMgr.getOptionalFileRef(*I);
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benlangmuir wrote:

Having `*Entry` on the next line without checking isn't great, but obviously not a new issue in this PR you need to fix.

https://github.com/llvm/llvm-project/pull/110014