Extract and refactor clang tidy CMake logic

Extracts the clang tidy block and does some tidying to simplify the
logic around it.

Add a clang-tidy file to handle all of our suppressed and active
warnings

.clang-tidy

+# Yaml file format
+Checks: >
+  *,
+  -abseil-*,-android-*,-altera-*,-fuchsia-*,-llvmlibc-*,-objc-*,
+  -google-build-using-namespace,
+  -google-readability-braces-around-statements,-hicpp-braces-around-statements,-readability-braces-around-statements,
+  -modernize-use-trailing-return-type,
+  -readability-implicit-bool-conversion
+
+# Skip the following family of checks (for perf as we don't touch these libs at all):
+# abseil-*
+# android-*
+# altera-*
+# fuchsia-*
+# llvmlibc-*
+# objc-*
+
+# The following checks are additionally disabled above:
+# -google-build-using-namespace                 Useful for headers, but we can't filter out .cpp where it's used frequently
+
+# -google-readability-braces-around-statements  We use if blocks without braces throughout
+# -readability-braces-around-statements         Ditto
+# -hicpp-braces-around-statements               Ditto
+
+# -modernize-use-trailing-return-type           We use the old style throughout
+
+# -readability-implicit-bool-conversion         Allow if(!ptr) rather than (ptr==nullptr)
+

buildconfig/CMake/ClangTidy.cmake

+option(ENABLE_CLANG_TIDY "Add clang-tidy automatically to builds")
+
+if(ENABLE_CLANG_TIDY)
+    option(APPLY_CLANG_TIDY_FIX "Apply fixes found through clang-tidy checks" OFF)
+
+    find_program(
+        CLANG_TIDY_EXE
+        NAMES
+            "clang-tidy-14"
+            "clang-tidy-13"
+            "clang-tidy-12"
+            "clang-tidy-11"
+            "clang-tidy-10"
+            "clang-tidy-9"
+            "clang-tidy"
+        PATHS /usr/local/opt/llvm/bin
+    )
+
+    if(NOT CLANG_TIDY_EXE)
+        message(FATAL_ERROR "Clang Tidy was enabled, but the EXE could not be found.")
+    endif()
+
+    message(STATUS "clang-tidy found: ${CLANG_TIDY_EXE}")
+
+    set(CLANG_TIDY_CHECKS "${DEFAULT_CLANG_TIDY_CHECKS}"
+        CACHE STRING "Select checks to perform")
+
+    if(CLANG_TIDY_CHECKS STREQUAL "")
+        # use default checks if empty to avoid errors
+        set(CLANG_TIDY_CHECKS
+            "${DEFAULT_CLANG_TIDY_CHECKS}"
+            CACHE STRING "Select checks to perform" FORCE)
+    endif()
+
+    set(CMAKE_CXX_CLANG_TIDY "${CLANG_TIDY_EXE}" CACHE STRING "" FORCE)
+    if (APPLY_CLANG_TIDY_FIX)
+        message(WARNING "You must build with a single thread (-j1) to avoid duplicate fixes in files or use run-clang-tidy.py")
+        set(CMAKE_CXX_CLANG_TIDY "${CMAKE_CXX_CLANG_TIDY};-fix"
+            CACHE STRING "" FORCE)
+    endif()
+else()
+    # Turn off
+    set(CMAKE_CXX_CLANG_TIDY  "" CACHE STRING "" FORCE)
+endif()

buildconfig/CMake/CommonSetup.cmake

@@ -321,64 +321,7 @@ endif()
 # ##############################################################################
 # Configure clang-tidy if the tool is found
 # ##############################################################################
-
-if(CMAKE_VERSION VERSION_GREATER "3.5")
-  set(DEFAULT_CLANG_TIDY_CHECKS
-      "-*,performance-for-range-copy,performance-unnecessary-copy-initialization,modernize-use-override,modernize-use-nullptr,modernize-loop-convert,modernize-use-bool-literals,modernize-deprecated-headers,misc-*,-misc-unused-parameters"
-  )
-  option(ENABLE_CLANG_TIDY "Add clang-tidy automatically to builds")
-  if(ENABLE_CLANG_TIDY)
-    find_program(
-      CLANG_TIDY_EXE
-      NAMES "clang-tidy"
-      PATHS /usr/local/opt/llvm/bin
-    )
-    if(CLANG_TIDY_EXE)
-      message(STATUS "clang-tidy found: ${CLANG_TIDY_EXE}")
-      set(CLANG_TIDY_CHECKS
-          "${DEFAULT_CLANG_TIDY_CHECKS}"
-          CACHE STR "Select checks to perform"
-      )
-      option(APPLY_CLANG_TIDY_FIX "Apply fixes found through clang-tidy checks"
-             OFF
-      )
-      if(CLANG_TIDY_CHECKS STREQUAL "")
-        # use default checks if empty to avoid errors
-        set(CLANG_TIDY_CHECKS
-            "${DEFAULT_CLANG_TIDY_CHECKS}"
-            CACHE STR "Select checks to perform" FORCE
-        )
-      endif()
-      if(APPLY_CLANG_TIDY_FIX)
-        set(CMAKE_CXX_CLANG_TIDY
-            "${CLANG_TIDY_EXE};-checks=${CLANG_TIDY_CHECKS};-header-filter='${CMAKE_SOURCE_DIR}/*';-fix"
-            CACHE STRING "" FORCE
-        )
-      else()
-        set(CMAKE_CXX_CLANG_TIDY
-            "${CLANG_TIDY_EXE};-checks=${CLANG_TIDY_CHECKS};-header-filter='${CMAKE_SOURCE_DIR}/*'"
-            CACHE STRING "" FORCE
-        )
-      endif()
-    else()
-      message(AUTHOR_WARNING "clang-tidy not found!")
-      set(CMAKE_CXX_CLANG_TIDY
-          ""
-          CACHE STRING "" FORCE
-      ) # delete it
-    endif()
-  else()
-    set(CMAKE_CXX_CLANG_TIDY
-        ""
-        CACHE STRING "" FORCE
-    ) # delete it
-  endif()
-else()
-  message(
-    AUTHOR_WARNING
-      "Using cmake version 3.5 or below. Clang-tidy is not supported!"
-  )
-endif()
+include(ClangTidy)
 
 # ##############################################################################
 # Setup cppcheck