[clang] [clang-format] Add MainIncludeChar option. (PR #78752)

[Björn Schäpers via cfe-commits]

================
@@ -151,6 +151,21 @@ struct IncludeStyle {
   /// before any other include.
   /// \version 10
   std::string IncludeIsMainSourceRegex;
+
+  /// Character to consider in the include directives for the main header.
+  enum MainIncludeCharDiscriminator {
+    /// Main include uses quotes: ``#include "foo.hpp"``
+    MICD_Quote,
+    /// Main include uses brackets: ``#include <foo.hpp>``
+    MICD_Bracket,
+    /// Main include uses either quotes or brackets.
----------------
HazardyKnusperkeks wrote:

```suggestion
    /// Main include uses angle brackets: ``#include <foo.hpp>``
    MICD_AngleBracket,
    /// Main include uses either quotes or angle brackets.
```

Brackets are `[` and `]`.

https://github.com/llvm/llvm-project/pull/78752