diff --git a/clang-tidy/ClangTidyOptions.cpp b/clang-tidy/ClangTidyOptions.cpp
index 148593d..a4bfe04 100644
--- a/clang-tidy/ClangTidyOptions.cpp
+++ b/clang-tidy/ClangTidyOptions.cpp
@@ -85,6 +85,7 @@ template <> struct MappingTraits<ClangTidyOptions> {
     IO.mapOptional("Checks", Options.Checks);
     IO.mapOptional("HeaderFilterRegex", Options.HeaderFilterRegex);
     IO.mapOptional("AnalyzeTemporaryDtors", Options.AnalyzeTemporaryDtors);
+    IO.mapOptional("User", Options.User);
     IO.mapOptional("CheckOptions", NOpts->Options);
   }
 };
@@ -109,6 +110,8 @@ ClangTidyOptions::mergeWith(const ClangTidyOptions &Other) const {
     Result.HeaderFilterRegex = Other.HeaderFilterRegex;
   if (Other.AnalyzeTemporaryDtors)
     Result.AnalyzeTemporaryDtors = Other.AnalyzeTemporaryDtors;
+  if (Other.User)
+    Result.User = Other.User;
 
   for (const auto &KeyValue : Other.CheckOptions)
     Result.CheckOptions[KeyValue.first] = KeyValue.second;
@@ -118,11 +121,11 @@ ClangTidyOptions::mergeWith(const ClangTidyOptions &Other) const {
 
 FileOptionsProvider::FileOptionsProvider(
     const ClangTidyGlobalOptions &GlobalOptions,
-    const ClangTidyOptions &FallbackOptions,
+    const ClangTidyOptions &DefaultOptions,
     const ClangTidyOptions &OverrideOptions)
-    : DefaultOptionsProvider(GlobalOptions, FallbackOptions),
+    : DefaultOptionsProvider(GlobalOptions, DefaultOptions),
       OverrideOptions(OverrideOptions) {
-  CachedOptions[""] = FallbackOptions.mergeWith(OverrideOptions);
+  CachedOptions[""] = DefaultOptions.mergeWith(OverrideOptions);
 }
 
 static const char ConfigFileName[] = ".clang-tidy";
@@ -177,7 +180,6 @@ llvm::ErrorOr<ClangTidyOptions>
 FileOptionsProvider::TryReadConfigFile(StringRef Directory) {
   assert(!Directory.empty());
 
-  ClangTidyOptions Options = DefaultOptionsProvider::getOptions(Directory);
   if (!llvm::sys::fs::is_directory(Directory))
     return make_error_code(llvm::errc::not_a_directory);
 
@@ -201,9 +203,15 @@ FileOptionsProvider::TryReadConfigFile(StringRef Directory) {
   // redirection.
   if ((*Text)->getBuffer().empty())
     return make_error_code(llvm::errc::no_such_file_or_directory);
-  if (std::error_code EC = parseConfiguration((*Text)->getBuffer(), Options))
-    return EC;
-  return Options.mergeWith(OverrideOptions);
+  llvm::ErrorOr<ClangTidyOptions> ParsedOptions =
+      parseConfiguration((*Text)->getBuffer());
+  if (ParsedOptions) {
+    ClangTidyOptions Defaults = DefaultOptionsProvider::getOptions(Directory);
+    // Only use checks from the config file.
+    Defaults.Checks = None;
+    return Defaults.mergeWith(*ParsedOptions).mergeWith(OverrideOptions);
+  }
+  return ParsedOptions.getError();
 }
 
 /// \brief Parses -line-filter option and stores it to the \c Options.
@@ -214,11 +222,13 @@ std::error_code parseLineFilter(StringRef LineFilter,
   return Input.error();
 }
 
-std::error_code parseConfiguration(StringRef Config,
-                                   clang::tidy::ClangTidyOptions &Options) {
+llvm::ErrorOr<ClangTidyOptions> parseConfiguration(StringRef Config) {
   llvm::yaml::Input Input(Config);
+  ClangTidyOptions Options;
   Input >> Options;
-  return Input.error();
+  if (Input.error())
+    return Input.error();
+  return Options;
 }
 
 std::string configurationAsText(const ClangTidyOptions &Options) {
diff --git a/clang-tidy/ClangTidyOptions.h b/clang-tidy/ClangTidyOptions.h
index 3c2251c..82a740c 100644
--- a/clang-tidy/ClangTidyOptions.h
+++ b/clang-tidy/ClangTidyOptions.h
@@ -55,6 +55,7 @@ struct ClangTidyOptions {
     Options.Checks = "";
     Options.HeaderFilterRegex = "";
     Options.AnalyzeTemporaryDtors = false;
+    Options.User = llvm::None;
     return Options;
   }
 
@@ -72,6 +73,12 @@ struct ClangTidyOptions {
   /// \brief Turns on temporary destructor-based analysis.
   llvm::Optional<bool> AnalyzeTemporaryDtors;
 
+  /// \brief Specifies the name or e-mail of the user running clang-tidy.
+  ///
+  /// This option is used, for example, to place the correct user name in TODO()
+  /// comments in the relevant check.
+  llvm::Optional<std::string> User;
+
   typedef std::pair<std::string, std::string> StringPair;
   typedef std::map<std::string, std::string> OptionMap;
 
@@ -121,19 +128,19 @@ public:
   /// \param GlobalOptions are just stored and returned to the caller of
   /// \c getGlobalOptions.
   ///
-  /// \param FallbackOptions are used in case there's no corresponding
+  /// \param DefaultOptions are used for all settings not specified in a
   /// .clang-tidy file.
   ///
   /// If any of the \param OverrideOptions fields are set, they will override
   /// whatever options are read from the configuration file.
   FileOptionsProvider(const ClangTidyGlobalOptions &GlobalOptions,
-                      const ClangTidyOptions &FallbackOptions,
+                      const ClangTidyOptions &DefaultOptions,
                       const ClangTidyOptions &OverrideOptions);
   const ClangTidyOptions &getOptions(llvm::StringRef FileName) override;
 
 private:
   /// \brief Try to read configuration file from \p Directory. If \p Directory
-  /// is empty, use the fallback value.
+  /// is empty, use the default value.
   llvm::ErrorOr<ClangTidyOptions> TryReadConfigFile(llvm::StringRef Directory);
 
   llvm::StringMap<ClangTidyOptions> CachedOptions;
@@ -144,9 +151,9 @@ private:
 std::error_code parseLineFilter(llvm::StringRef LineFilter,
                                 ClangTidyGlobalOptions &Options);
 
-/// \brief Parses configuration from JSON and stores it to the \p Options.
-std::error_code parseConfiguration(llvm::StringRef Config,
-                                   ClangTidyOptions &Options);
+/// \brief Parses configuration from JSON and returns \c ClangTidyOptions or an
+/// error.
+llvm::ErrorOr<ClangTidyOptions> parseConfiguration(llvm::StringRef Config);
 
 /// \brief Serializes configuration to a YAML-encoded string.
 std::string configurationAsText(const ClangTidyOptions &Options);
diff --git a/clang-tidy/google/TodoCommentCheck.cpp b/clang-tidy/google/TodoCommentCheck.cpp
index 5937f8f..26ad6b6 100644
--- a/clang-tidy/google/TodoCommentCheck.cpp
+++ b/clang-tidy/google/TodoCommentCheck.cpp
@@ -17,8 +17,9 @@ namespace readability {
 
 class TodoCommentCheck::TodoCommentHandler : public CommentHandler {
 public:
-  explicit TodoCommentHandler(TodoCommentCheck &Check)
-      : Check(Check), TodoMatch("^// *TODO(\\(.*\\))?:?( )?(.*)$") {}
+  TodoCommentHandler(TodoCommentCheck &Check, llvm::Optional<std::string> User)
+      : Check(Check), User(User ? *User : "unknown"),
+        TodoMatch("^// *TODO(\\(.*\\))?:?( )?(.*)$") {}
 
   bool HandleComment(Preprocessor &PP, SourceRange Range) override {
     StringRef Text =
@@ -35,12 +36,6 @@ public:
     if (!Username.empty())
       return false;
 
-    // If the username is missing put in the current user's name. Not ideal but
-    // works for running tidy locally.
-    // FIXME: Can we get this from a more reliable source?
-    const char *User = std::getenv("USER");
-    if (!User)
-      User = "unknown";
     std::string NewText = ("// TODO(" + Twine(User) + "): " + Comment).str();
 
     Check.diag(Range.getBegin(), "missing username/bug in TODO")
@@ -51,14 +46,14 @@ public:
 
 private:
   TodoCommentCheck &Check;
+  std::string User;
   llvm::Regex TodoMatch;
 };
 
 TodoCommentCheck::TodoCommentCheck(StringRef Name, ClangTidyContext *Context)
     : ClangTidyCheck(Name, Context),
-      Handler(llvm::make_unique<TodoCommentHandler>(*this)) {}
-
-TodoCommentCheck::~TodoCommentCheck() {}
+      Handler(llvm::make_unique<TodoCommentHandler>(
+          *this, Context->getOptions().User)) {}
 
 void TodoCommentCheck::registerPPCallbacks(CompilerInstance &Compiler) {
   Compiler.getPreprocessor().addCommentHandler(Handler.get());
diff --git a/clang-tidy/google/TodoCommentCheck.h b/clang-tidy/google/TodoCommentCheck.h
index 10e84a7..b3b49fd 100644
--- a/clang-tidy/google/TodoCommentCheck.h
+++ b/clang-tidy/google/TodoCommentCheck.h
@@ -22,7 +22,6 @@ namespace readability {
 class TodoCommentCheck : public ClangTidyCheck {
 public:
   TodoCommentCheck(StringRef Name, ClangTidyContext *Context);
-  ~TodoCommentCheck();
   void registerPPCallbacks(CompilerInstance &Compiler) override;
 
 private:
diff --git a/clang-tidy/tool/ClangTidyMain.cpp b/clang-tidy/tool/ClangTidyMain.cpp
index f11cbee..a9b29f6 100644
--- a/clang-tidy/tool/ClangTidyMain.cpp
+++ b/clang-tidy/tool/ClangTidyMain.cpp
@@ -17,6 +17,7 @@
 
 #include "../ClangTidy.h"
 #include "clang/Tooling/CommonOptionsParser.h"
+#include "llvm/Support/Process.h"
 
 using namespace clang::ast_matchers;
 using namespace clang::driver;
@@ -143,10 +144,14 @@ int clangTidyMain(int argc, const char **argv) {
     return 1;
   }
 
-  ClangTidyOptions FallbackOptions;
-  FallbackOptions.Checks = DefaultChecks;
-  FallbackOptions.HeaderFilterRegex = HeaderFilter;
-  FallbackOptions.AnalyzeTemporaryDtors = AnalyzeTemporaryDtors;
+  ClangTidyOptions DefaultOptions;
+  DefaultOptions.Checks = DefaultChecks;
+  DefaultOptions.HeaderFilterRegex = HeaderFilter;
+  DefaultOptions.AnalyzeTemporaryDtors = AnalyzeTemporaryDtors;
+  DefaultOptions.User = llvm::sys::Process::GetEnv("USER");
+  // USERNAME is used on Windows.
+  if (!DefaultOptions.User)
+    DefaultOptions.User = llvm::sys::Process::GetEnv("USERNAME");
 
   ClangTidyOptions OverrideOptions;
   if (Checks.getNumOccurrences() > 0)
@@ -157,7 +162,7 @@ int clangTidyMain(int argc, const char **argv) {
     OverrideOptions.AnalyzeTemporaryDtors = AnalyzeTemporaryDtors;
 
   auto OptionsProvider = llvm::make_unique<FileOptionsProvider>(
-      GlobalOptions, FallbackOptions, OverrideOptions);
+      GlobalOptions, DefaultOptions, OverrideOptions);
 
   std::string FileName = OptionsParser.getSourcePathList().front();
   ClangTidyOptions EffectiveOptions = OptionsProvider->getOptions(FileName);
diff --git a/unittests/clang-tidy/ClangTidyOptionsTest.cpp b/unittests/clang-tidy/ClangTidyOptionsTest.cpp
index 8b0fbc6..dd23045 100644
--- a/unittests/clang-tidy/ClangTidyOptionsTest.cpp
+++ b/unittests/clang-tidy/ClangTidyOptionsTest.cpp
@@ -55,15 +55,16 @@ TEST(ParseLineFilter, ValidFilter) {
 }
 
 TEST(ParseConfiguration, ValidConfiguration) {
-  ClangTidyOptions Options;
-  std::error_code Error = parseConfiguration("Checks: \"-*,misc-*\"\n"
-                                             "HeaderFilterRegex: \".*\"\n"
-                                             "AnalyzeTemporaryDtors: true\n",
-                                             Options);
-  EXPECT_FALSE(Error);
-  EXPECT_EQ("-*,misc-*", *Options.Checks);
-  EXPECT_EQ(".*", *Options.HeaderFilterRegex);
-  EXPECT_TRUE(*Options.AnalyzeTemporaryDtors);
+  llvm::ErrorOr<ClangTidyOptions> Options =
+      parseConfiguration("Checks: \"-*,misc-*\"\n"
+                         "HeaderFilterRegex: \".*\"\n"
+                         "AnalyzeTemporaryDtors: true\n"
+                         "User: some.user");
+  EXPECT_TRUE(!!Options);
+  EXPECT_EQ("-*,misc-*", *Options->Checks);
+  EXPECT_EQ(".*", *Options->HeaderFilterRegex);
+  EXPECT_TRUE(*Options->AnalyzeTemporaryDtors);
+  EXPECT_EQ("some.user", *Options->User);
 }
 
 } // namespace test