[clang] [clang-format] Add `AllowShortNamespacesOnASingleLine` option (PR #105597)

[Owen Pan via cfe-commits]

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@@ -916,6 +983,21 @@ class LineJoiner {
     return 1 + I[1]->Last->TotalLength + 1 + I[2]->Last->TotalLength <= Limit;
   }
 
+  bool nextNLinesFitInto(SmallVectorImpl<AnnotatedLine *>::const_iterator I,
+                         SmallVectorImpl<AnnotatedLine *>::const_iterator E,
+                         unsigned Limit) {
+    unsigned JoinedLength = 0;
+    for (auto J = I + 1; J != E; ++J) {
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owenca wrote:

```suggestion
    for (const auto *J = I + 1; J != E; ++J) {
```

https://github.com/llvm/llvm-project/pull/105597