[clang] [clang-format] Support BraceWrapping.AfterNamespace with AllowShortNamespacesOnASingleLine (PR #123010)

[Owen Pan via cfe-commits]

================
@@ -660,17 +672,18 @@ class LineJoiner {
 
       assert(Limit >= L1.Last->TotalLength + 3);
       const auto InnerLimit = Limit - L1.Last->TotalLength - 3;
-      const auto MergedLines = tryMergeNamespace(I + 1, E, InnerLimit);
+      const auto MergedLines =
+          tryMergeNamespace(BraceOpenLine + 1, E, InnerLimit);
       if (MergedLines == 0)
         return 0;
-      const auto N = MergedLines + 2;
+      const auto N = MergedLines + LinesToBeMerged;
       // Check if there is even a line after the inner result.
       if (std::distance(I, E) <= N)
         return 0;
       // Check that the line after the inner result starts with a closing brace
       // which we are permitted to merge into one line.
       if (I[N]->First->is(tok::r_brace) && !I[N]->First->MustBreakBefore &&
----------------
owenca wrote:

```suggestion
      if (I[N]->First->is(TT_NamespaceRBrace) &&
          !I[N]->First->MustBreakBefore &&
```

https://github.com/llvm/llvm-project/pull/123010