[clang] [clang] Add option to opt out of the missing_dependent_template_keyword diagnostic (PR #98613)

[Haojian Wu via cfe-commits]

https://github.com/hokein created https://github.com/llvm/llvm-project/pull/98613

After commit ce4aada6e2135e29839f672a6599db628b53295d, we observed many warnings in our internal codebase. It is 
 infeasible to fix all at once.

Currently, there is no way to disable this warning. This patch provides a way to disable it using the `-Wno-missing-dependent-template-keyword` flag.

>From d22741375619b2b134509049aad7958348abcc30 Mon Sep 17 00:00:00 2001
From: Haojian Wu <hokein.wu at gmail.com>
Date: Fri, 12 Jul 2024 12:26:07 +0200
Subject: [PATCH] [clang] Allow to opt out the
 missing_dependent_template_keyword diagnostic.

---
 clang/include/clang/Basic/DiagnosticParseKinds.td | 3 ++-
 clang/test/Misc/warning-flags.c                   | 3 +--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/clang/include/clang/Basic/DiagnosticParseKinds.td b/clang/include/clang/Basic/DiagnosticParseKinds.td
index 0bd2e35bf2e31..e00cd47411cb3 100644
--- a/clang/include/clang/Basic/DiagnosticParseKinds.td
+++ b/clang/include/clang/Basic/DiagnosticParseKinds.td
@@ -896,7 +896,8 @@ def missing_template_arg_list_after_template_kw : Extension<
   DefaultError;
 
 def ext_missing_dependent_template_keyword : ExtWarn<
-  "use 'template' keyword to treat '%0' as a dependent template name">;
+  "use 'template' keyword to treat '%0' as a dependent template name">,
+  InGroup<DiagGroup<"missing-dependent-template-keyword">>;
 
 def ext_extern_template : Extension<
   "extern templates are a C++11 extension">, InGroup<CXX11>;
diff --git a/clang/test/Misc/warning-flags.c b/clang/test/Misc/warning-flags.c
index 651a86fb6e226..7b993f6849363 100644
--- a/clang/test/Misc/warning-flags.c
+++ b/clang/test/Misc/warning-flags.c
@@ -18,10 +18,9 @@ This test serves two purposes:
 
 The list of warnings below should NEVER grow.  It should gradually shrink to 0.
 
-CHECK: Warnings without flags (65):
+CHECK: Warnings without flags (64):
 
 CHECK-NEXT:   ext_expected_semi_decl_list
-CHECK-NEXT:   ext_missing_dependent_template_keyword
 CHECK-NEXT:   ext_missing_whitespace_after_macro_name
 CHECK-NEXT:   ext_new_paren_array_nonconst
 CHECK-NEXT:   ext_plain_complex