cope with possible translation drift (#24842)

* cope with possible translation drift

* fix test

* don't shallow clone

* fix unit tests

* update code comments

* more code comment corrections

* more code comment

* feedbacked

lib/create-tree.js

@@ -8,7 +8,7 @@ const __dirname = path.dirname(fileURLToPath(import.meta.url))
 const _basePaths = new Map()
 // Return a full directory based on __dirname from a specific language directory.
 // This function is memoized with a simple global cache object.
-function getBasePath(directory) {
+export function getBasePath(directory) {
   if (!_basePaths.has(directory)) {
     _basePaths.set(directory, path.posix.join(__dirname, '..', directory, 'content'))
   }