[clang] [clang-format] allow short function body on a single line (PR #151428)

[Lidong Yan via cfe-commits]

================
@@ -1921,6 +1921,10 @@ void UnwrappedLineParser::parseStructuralElement(
           }
         } else if (Style.BraceWrapping.AfterFunction) {
           addUnwrappedLine();
+        } else if (Style.AllowShortFunctionBodiesOnASingleLine) {
+          // Wrap the left brace here; we'll try to merge it back
----------------
brandb97 wrote:

If `Style.AllowShortFunctionBodiesOnSingleLine = true`, I modified UnwrappedLineParser to parse
```
int main() {
  //...
}
```
into unwrapped lines ["int main()", "{", ..., "}"], not ["int main() {", ..., "}"] as usual. If clang-format can't put function body on a single line, I want to merge "int main()" and "{" back if possible.

https://github.com/llvm/llvm-project/pull/151428