Restore order in clang-tidy section of release notes

Major changes are introduction of subsubsections to prevent people
putting new entries in wrong places. I also polished line length and
highlighting.

Patch by Eugene Zelenko!

clang-tools-extra/docs/ReleaseNotes.rst

@@ -67,6 +67,9 @@ The improvements are...
 Improvements to clang-tidy
 --------------------------
 
+New checks
+^^^^^^^^^^
+
 - New :doc:`bugprone-bad-signal-to-kill-thread
   <clang-tidy/checks/bugprone-bad-signal-to-kill-thread>` check.
 
@@ -89,28 +92,20 @@ Improvements to clang-tidy
   <clang-tidy/checks/bugprone-not-null-terminated-result>` check
 
   Finds function calls where it is possible to cause a not null-terminated
-  result. Usually the proper length of a string is ``strlen(str) + 1`` or equal
-  length of this expression, because the null terminator needs an extra space.
-  Without the null terminator it can result in undefined behaviour when the
-  string is read.
+  result.
 
 - New :doc:`bugprone-signed-char-misuse
   <clang-tidy/checks/bugprone-signed-char-misuse>` check.
 
-  Finds ``signed char`` -> integer conversions which might indicate a programming
-  error.
+  Finds ``signed char`` to integer conversions which might indicate a
+  programming error.
 
 - New :doc:`cert-mem57-cpp
   <clang-tidy/checks/cert-mem57-cpp>` check.
 
   Checks if an object of type with extended alignment is allocated by using
   the default ``operator new``.
 
-- New alias :doc:`cert-pos44-c
-  <clang-tidy/checks/cert-pos44-c>` to
-  :doc:`bugprone-bad-signal-to-kill-thread
-  <clang-tidy/checks/bugprone-bad-signal-to-kill-thread>` was added.
-
 - New :doc:`cert-oop58-cpp
   <clang-tidy/checks/cert-oop58-cpp>` check.
 
@@ -120,6 +115,9 @@ Improvements to clang-tidy
 - New :doc:`cppcoreguidelines-init-variables
   <clang-tidy/checks/cppcoreguidelines-init-variables>` check.
 
+  Checks whether there are local variables that are declared without an initial
+  value.
+
 - New :doc:`darwin-dispatch-once-nonstatic
   <clang-tidy/checks/darwin-dispatch-once-nonstatic>` check.
 
@@ -132,11 +130,6 @@ Improvements to clang-tidy
   Finds uses of deprecated Googletest APIs with names containing ``case`` and
   replaces them with equivalent APIs with ``suite``.
 
-- Improved :doc:`hicpp-signed-bitwise
-  <clang-tidy/checks/hicpp-signed-bitwise>` check.
-
-  The check now supports the ``IgnorePositiveIntegerLiterals`` option.
-
 - New :doc:`linuxkernel-must-use-errs
   <clang-tidy/checks/linuxkernel-must-use-errs>` check.
 
@@ -166,69 +159,88 @@ Improvements to clang-tidy
   Finds types that could be made trivially-destructible by removing out-of-line
   defaulted destructor declarations.
 
-- The :doc:`modernize-use-using
-  <clang-tidy/checks/modernize-use-using>` check now converts typedefs containing
-  struct definitions and multiple comma-separated types.
+- New :doc:`readability-make-member-function-const
+  <clang-tidy/checks/readability-make-member-function-const>` check.
+
+  Finds non-static member functions that can be made ``const``
+  because the functions don't use ``this`` in a non-const way.
+
+- New :doc:`readability-redundant-access-specifiers
+  <clang-tidy/checks/readability-redundant-access-specifiers>` check.
+
+  Finds classes, structs, and unions that contain redundant member
+  access specifiers.
+
+New aliases
+^^^^^^^^^^^
+
+- New alias :doc:`cert-pos44-c
+  <clang-tidy/checks/cert-pos44-c>` to
+  :doc:`bugprone-bad-signal-to-kill-thread
+  <clang-tidy/checks/bugprone-bad-signal-to-kill-thread>` was added.
+
+Changes in existing checks
+^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 - Improved :doc:`bugprone-posix-return
   <clang-tidy/checks/bugprone-posix-return>` check.
 
-  Now also checks if any calls to ``pthread_*`` functions expect negative return
-  values.
+  Now also checks if any calls to ``pthread_*`` functions expect negative
+  return values.
 
-- The 'objc-avoid-spinlock' check was renamed to :doc:`darwin-avoid-spinlock
-  <clang-tidy/checks/darwin-avoid-spinlock>`
+- Improved :doc:`hicpp-signed-bitwise
+  <clang-tidy/checks/hicpp-signed-bitwise>` check.
+
+  The check now supports the `IgnorePositiveIntegerLiterals` option.
+
+- Improved :doc:`modernize-avoid-bind
+  <clang-tidy/checks/modernize-avoid-bind>` check.
+
+  The check now supports supports diagnosing and fixing arbitrary callables
+  instead of only simple free functions. The `PermissiveParameterList` option
+  has also been added to address situations where the existing fix-it logic
+  would sometimes generate code that no longer compiles.
 
 - The :doc:`modernize-use-equals-default
   <clang-tidy/checks/modernize-use-equals-default>` fix no longer adds
   semicolons where they would be redundant.
 
-- New :doc:`readability-redundant-access-specifiers
-  <clang-tidy/checks/readability-redundant-access-specifiers>` check.
+- Improved :doc:`modernize-use-override
+  <clang-tidy/checks/modernize-use-override>` check.
 
-  Finds classes, structs, and unions that contain redundant member
-  access specifiers.
+  The check now supports the `AllowOverrideAndFinal` option to eliminate
+  conflicts with `gcc -Wsuggest-override` or `gcc -Werror=suggest-override`.
+
+- The :doc:`modernize-use-using
+  <clang-tidy/checks/modernize-use-using>` check now converts typedefs
+  containing struct definitions and multiple comma-separated types.
 
 - Improved :doc:`readability-magic-numbers
   <clang-tidy/checks/readability-magic-numbers>` check.
 
-  The check now supports the ``IgnoreBitFieldsWidths`` option to suppress
+  The check now supports the `IgnoreBitFieldsWidths` option to suppress
   the warning for numbers used to specify bit field widths.
 
   The check was updated to eliminate some false positives (such as using
   class enumeration as non-type template parameters, or the synthetically
-  computed lengh of a static user string literal.)
-
-- New :doc:`readability-make-member-function-const
-  <clang-tidy/checks/readability-make-member-function-const>` check.
-
-  Finds non-static member functions that can be made ``const``
-  because the functions don't use ``this`` in a non-const way.
-
-- Improved :doc:`modernize-use-override
-  <clang-tidy/checks/modernize-use-override>` check.
-
-  The check now supports the ``AllowOverrideAndFinal`` option to eliminate
-  conflicts with ``gcc -Wsuggest-override`` or ``gcc -Werror=suggest-override``.
+  computed length of a static user string literal.)
 
 - Improved :doc:`readability-redundant-member-init
   <clang-tidy/checks/readability-redundant-member-init>` check.
 
-  The check  now supports the ``IgnoreBaseInCopyConstructors`` option to avoid
+  The check  now supports the `IgnoreBaseInCopyConstructors` option to avoid
   `"base class 'Foo' should be explicitly initialized in the copy constructor"`
-  warnings or errors with ``gcc -Wextra`` or ``gcc -Werror=extra``.
+  warnings or errors with `gcc -Wextra` or `gcc -Werror=extra`.
 
 - The :doc:`readability-redundant-string-init
   <clang-tidy/checks/readability-redundant-string-init>` check now supports a
   `StringNames` option enabling its application to custom string classes.
 
-- Improved :doc:`modernize-avoid-bind
-  <clang-tidy/checks/modernize-avoid-bind>` check.
+Renamed checks
+^^^^^^^^^^^^^^
 
-  The check now supports supports diagnosing and fixing arbitrary callables instead of
-  only simple free functions. The `PermissiveParameterList` option has also been
-  added to address situations where the existing fix-it logic would sometimes generate
-  code that no longer compiles.
+- The 'objc-avoid-spinlock' check was renamed to :doc:`darwin-avoid-spinlock
+  <clang-tidy/checks/darwin-avoid-spinlock>`
 
 Improvements to include-fixer
 -----------------------------