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

[Owen Pan via cfe-commits]

================
@@ -616,6 +626,71 @@ class LineJoiner {
     return 1;
   }
 
+  unsigned tryMergeNamespace(SmallVectorImpl<AnnotatedLine *>::const_iterator I,
+                             SmallVectorImpl<AnnotatedLine *>::const_iterator E,
+                             unsigned Limit) {
+    if (Limit == 0)
+      return 0;
+    assert(I[1]);
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owenca wrote:

```suggestion

    assert(I[1]);
```

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