[clang] [clang-format]: Add `Custom` to `ShortFunctionStyle`; add new AllowShortFunctionsOnASingleLineOptions for granular setup (PR #134337)

[Owen Pan via cfe-commits]

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@@ -293,15 +293,14 @@ class LineJoiner {
 
     auto ShouldMergeShortFunctions = [this, &I, &NextLine, PreviousLine,
                                       TheLine]() {
-      if (Style.AllowShortFunctionsOnASingleLine == FormatStyle::SFS_All)
+      if (Style.AllowShortFunctionsOnASingleLine.Other)
         return true;
-      if (Style.AllowShortFunctionsOnASingleLine >= FormatStyle::SFS_Empty &&
+      if (Style.AllowShortFunctionsOnASingleLine.Empty &&
           NextLine.First->is(tok::r_brace)) {
         return true;
       }
 
-      if (Style.AllowShortFunctionsOnASingleLine &
-          FormatStyle::SFS_InlineOnly) {
+      if (Style.AllowShortFunctionsOnASingleLine.Inline) {
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owenca wrote:

See https://github.com/llvm/llvm-project/pull/134337#discussion_r2029943820.

https://github.com/llvm/llvm-project/pull/134337