[clang] [clang-tools-extra] [clangd][clang-tidy] Factor out mergeFixits() logic and reuse it in clangd (PR #208682)

[Baranov Victor via cfe-commits]

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@@ -476,3 +477,58 @@ EditedSource::getActionForOffset(FileOffset Offs) {
 
   return FileEdits.end();
 }
+
+namespace clang {
+namespace edit {
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vbvictor wrote:

We can merge namespaces

https://github.com/llvm/llvm-project/pull/208682