On Windows, the cli_basename function should treat both '/' and '\' as path
separators. Most Windows APIs also accept both.
On Linux/Unix, it makes sense when using a filepath that is more for
informational purposes or where it may have come from a Windows system,
to treat the '\' as a path separator.
But in situations where the the path is needed for some critical action,
like moving or deleting a file, we can't treat it as a path separator.
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