Index: ClangTidy.cpp
===================================================================
--- ClangTidy.cpp
+++ ClangTidy.cpp
@@ -608,8 +608,55 @@
                         raw_ostream &OS) {
   TranslationUnitDiagnostics TUD;
   TUD.MainSourceFile = MainFilePath;
+
+  FileManager *Files = new FileManager(FileSystemOptions());
+  vfs::FileSystem &FileSystem = *Files->getVirtualFileSystem();
+  auto InitialWorkingDir = FileSystem.getCurrentWorkingDirectory();
+  if (!InitialWorkingDir)
+    llvm::report_fatal_error("Cannot get current working path.");
+
+  llvm::StringMap<Replacements> FileReplacements;
+  llvm::StringMap<ClangTidyError> SingleErrors;
   for (const auto &Error : Errors) {
-    tooling::Diagnostic Diag = Error;
+    if (!Error.BuildDirectory.empty())
+      FileSystem.setCurrentWorkingDirectory(Error.BuildDirectory);
+
+    SmallString<128> ErrorAbsoluteFilePath = (StringRef)Error.Message.FilePath;
+    Files->makeAbsolutePath(ErrorAbsoluteFilePath);
+    if (SingleErrors.find(ErrorAbsoluteFilePath) == SingleErrors.end()) {
+      ClangTidyError AbsoluteError = Error;
+      AbsoluteError.Message.FilePath = ErrorAbsoluteFilePath.str();
+      AbsoluteError.Fix.clear();
+      SingleErrors.insert(std::pair<StringRef, ClangTidyError>(
+          ErrorAbsoluteFilePath, AbsoluteError));
+    }
+
+    for (const auto &FileAndReplacements : Error.Fix) {
+      for (const auto &Repl : FileAndReplacements.second) {
+        SmallString<128> FixAbsoluteFilePath = Repl.getFilePath();
+        Files->makeAbsolutePath(FixAbsoluteFilePath);
+
+        tooling::Replacement R(FixAbsoluteFilePath, Repl.getOffset(),
+                               Repl.getLength(), Repl.getReplacementText());
+
+        FileReplacements[R.getFilePath()].add(R);
+      }
+    }
+
+    FileSystem.setCurrentWorkingDirectory(InitialWorkingDir.get());
+  }
+
+  for (const auto &FileAndReplacements : FileReplacements) {
+    StringRef File = FileAndReplacements.first();
+    Replacements Repls = FileAndReplacements.second;
+
+    ClangTidyError AbsoluteError = SingleErrors.find(File)->second;
+    if (SingleErrors.find(File) == SingleErrors.end())
+      llvm::report_fatal_error("Cannot find the containing ClangTidyError.");
+
+    AbsoluteError.Fix.insert(std::pair<StringRef, Replacements>(File, Repls));
+
+    tooling::Diagnostic Diag = AbsoluteError;
     TUD.Diagnostics.insert(TUD.Diagnostics.end(), Diag);
   }