clang-format improvements (#1251)

* clang-format improvements

- Add a clang-format linter check to the PR pipeline
- Apply clang-format to files where the linter initially failed
- Remove `CommentPragmas` from `.clang-format`
- Remove all `// clang-format off` and `// NO-FORMAT` as they are not needed
- Remove a commented out `GSL_SUPPRESS`

* clang-format 20

* pipeline fail

* Update .github/workflows/clang-format.yml

Co-authored-by: Carson Radtke <nosrac925@gmail.com>

* output used clang-format version

* installed version is 18 which replaces "GSL_SUPPRESS(bounds.1)" with "GSL_SUPPRESS(bounds .1)"

* only include/gsl, not include

to prevent formatting of include/CMakeLists.txt

* apply clang-format[-20]

In a VS2026 developer command prompt I ran `clang-format -i include\gsl\* --assume-filename x.cpp`. This was necessary because VS GUI does not format files without an extension :(. Please note that `--assume-filename` is necessary here, otherwise the files will not be formatted. Surprisingly the behaviour for the formatter differs from the behaviour of `lang-format(-20) --dry-run --Werror include/gsl/*` where clang-format recognizes that the files is C++.

* change "#if 0" back to original version with comments only

* formatting scripts for windows and linux

for linux with linter (shfmt and shellcheck)

* add WhitespaceSensitiveMacros: [GSL_SUPPRESS]

* provide path for clang-format (Windows)

Currently not clear to me:
On my personal computer at home, when I start "Developer Command Prompt for VS18", I can run `clang-format` without providing the path.
On my managed (domain) company computer, when I start "Developer Command Prompt for VS18", I can NOT run `clang-format` without providing the path. I need to call `"%VCINSTALLDIR%Tools\Llvm\bin\clang-format"`.
I have no idea what the difference is. At least the version `"%VCINSTALLDIR%Tools\Llvm\bin\clang-format"` works on both computers, so I add the path.

---------

Co-authored-by: Werner Henze <w.henze@avm.de>
Co-authored-by: Carson Radtke <nosrac925@gmail.com>
Co-authored-by: Werner Henze <werner.henze+gitcommits@posteo.de>

include/gsl/util

@@ -21,8 +21,8 @@
 
 #include <array>
 #include <cstddef>          // for ptrdiff_t, size_t
-#include <limits>           // for numeric_limits
 #include <initializer_list> // for initializer_list
+#include <limits>           // for numeric_limits
 #include <type_traits>      // for is_signed, integral_constant
 #include <utility>          // for exchange, forward
 
@@ -100,18 +100,21 @@ template <class F>
 class final_action
 {
 public:
-    explicit final_action(const F& ff) noexcept : f{ff} { }
-    explicit final_action(F&& ff) noexcept : f{std::move(ff)} { }
+    explicit final_action(const F& ff) noexcept : f{ff} {}
+    explicit final_action(F&& ff) noexcept : f{std::move(ff)} {}
 
-    ~final_action() noexcept { if (invoke) f(); }
+    ~final_action() noexcept
+    {
+        if (invoke) f();
+    }
 
     final_action(final_action&& other) noexcept
         : f(std::move(other.f)), invoke(std::exchange(other.invoke, false))
-    { }
+    {}
 
-    final_action(const final_action&)   = delete;
+    final_action(const final_action&) = delete;
     void operator=(const final_action&) = delete;
-    void operator=(final_action&&)      = delete;
+    void operator=(final_action&&) = delete;
 
 private:
     F f;
@@ -127,10 +130,7 @@ GSL_NODISCARD auto finally(F&& f) noexcept
 
 // narrow_cast(): a searchable way to do narrowing casts of values
 template <class T, class U>
-// clang-format off
-GSL_SUPPRESS(type.1) // NO-FORMAT: attribute
-    // clang-format on
-    constexpr T narrow_cast(U&& u) noexcept
+GSL_SUPPRESS(type.1) constexpr T narrow_cast(U&& u) noexcept
 {
     return static_cast<T>(std::forward<U>(u));
 }
@@ -139,23 +139,17 @@ GSL_SUPPRESS(type.1) // NO-FORMAT: attribute
 // at() - Bounds-checked way of accessing builtin arrays, std::array, std::vector
 //
 template <class T, std::size_t N>
-// clang-format off
-GSL_SUPPRESS(bounds.4) // NO-FORMAT: attribute
-GSL_SUPPRESS(bounds.2) // NO-FORMAT: attribute
-    // clang-format on
-    constexpr T& at(T (&arr)[N], const index i)
+GSL_SUPPRESS(bounds.4) GSL_SUPPRESS(bounds.2) constexpr T& at(T (&arr)[N], const index i)
 {
-    static_assert(N <= static_cast<std::size_t>((std::numeric_limits<std::ptrdiff_t>::max)()), "We only support arrays up to PTRDIFF_MAX bytes.");
+    static_assert(N <= static_cast<std::size_t>((std::numeric_limits<std::ptrdiff_t>::max)()),
+                  "We only support arrays up to PTRDIFF_MAX bytes.");
     Expects(i >= 0 && i < narrow_cast<index>(N));
     return arr[narrow_cast<std::size_t>(i)];
 }
 
 template <class Cont>
-// clang-format off
-GSL_SUPPRESS(bounds.4) // NO-FORMAT: attribute
-GSL_SUPPRESS(bounds.2) // NO-FORMAT: attribute
-    // clang-format on
-    constexpr auto at(Cont& cont, const index i) -> decltype(cont[cont.size()])
+GSL_SUPPRESS(bounds.4) GSL_SUPPRESS(bounds.2) constexpr auto at(Cont& cont, const index i)
+    -> decltype(cont[cont.size()])
 {
     Expects(i >= 0 && i < narrow_cast<index>(cont.size()));
     using size_type = decltype(cont.size());
@@ -163,17 +157,18 @@ GSL_SUPPRESS(bounds.2) // NO-FORMAT: attribute
 }
 
 template <class T>
-// clang-format off
-GSL_SUPPRESS(bounds.1) // NO-FORMAT: attribute
-    // clang-format on
-    constexpr T at(const std::initializer_list<T> cont, const index i)
+GSL_SUPPRESS(bounds.1) constexpr T at(const std::initializer_list<T> cont, const index i)
 {
     Expects(i >= 0 && i < narrow_cast<index>(cont.size()));
     return *(cont.begin() + i);
 }
 
-template <class T, std::enable_if_t<std::is_move_assignable<T>::value && std::is_move_constructible<T>::value>>
-void swap(T& a, T& b) { std::swap(a, b); }
+template <class T, std::enable_if_t<std::is_move_assignable<T>::value &&
+                                    std::is_move_constructible<T>::value>>
+void swap(T& a, T& b)
+{
+    std::swap(a, b);
+}
 
 #if defined(__cpp_lib_span) && __cpp_lib_span >= 202002L
 template <class T, std::size_t extent = std::dynamic_extent>