[clang-tidy] add an overload for diag method that allows users to provide a diagnostic name rather than using the check name when building a diagnostic.

[JonasToth]

What is the reason you want this change to happen? I think this gives the chance to create inconsistencies which we should avoid.

[htl]

In D59318#1430829, @JonasToth wrote:

What is the reason you want this change to happen? I think this gives the chance to create inconsistencies which we should avoid.

Sorry this was a bit rushed. I was trying to pass some metadata in the diagnostic name so that another tool that uses the diagnostic name can perform some conditional evaluation based on the data. I will try coming up with a better plan and design for such a change.

Thank you

clang-tools-extra/clang-tidy/ClangTidy.h

public:
   /// \brief ``ClangTidyChecks`` that register ASTMatchers should do the actual
   /// work in here.
   virtual void check(const ast_matchers::MatchFinder::MatchResult &Result) {}
 
   /// \brief Add a diagnostic with the check's name.
   DiagnosticBuilder diag(SourceLocation Loc, StringRef Description,
                          DiagnosticIDs::Level Level = DiagnosticIDs::Warning);
 
+  /// \brief Add a diagnostic with a user-specified name.
+  ///
+  /// Similar to the method above, but allows user to specify a DiagnosticName
+  /// of the Diagnostic created.
+  DiagnosticBuilder diag(StringRef DiagnosticName, SourceLocation Loc,
+                         StringRef Description,
+                         DiagnosticIDs::Level Level = DiagnosticIDs::Warning);
+
   /// \brief Should store all options supported by this check with their
   /// current values or default values for options that haven't been overridden.
   ///
   /// The check should use ``Options.store()`` to store each option it supports
   /// whether it has the default value or it has been overridden.
   virtual void storeOptions(ClangTidyOptions::OptionMap &Options) {}
 
 private:

clang-tools-extra/clang-tidy/ClangTidy.cpp

ClangTidyOptions::OptionMap ClangTidyASTConsumerFactory::getCheckOptions() {
   return Options;
 }
 
 DiagnosticBuilder ClangTidyCheck::diag(SourceLocation Loc, StringRef Message,
                                        DiagnosticIDs::Level Level) {
   return Context->diag(CheckName, Loc, Message, Level);
 }
 
+DiagnosticBuilder ClangTidyCheck::diag(StringRef DiagnosticName,
+                                       SourceLocation Loc,
+                                       StringRef Description,
+                                       DiagnosticIDs::Level Level) {
+  return Context->diag(DiagnosticName, Loc, Description, Level);
+}
+
 void ClangTidyCheck::run(const ast_matchers::MatchFinder::MatchResult &Result) {
   // For historical reasons, checks don't implement the MatchFinder run()
   // callback directly. We keep the run()/check() distinction to avoid interface
   // churn, and to allow us to add cross-cutting logic in the future.
   check(Result);
 }
 
 OptionsView::OptionsView(StringRef CheckName,