regfilesin fault #158
Description
in FileSystem there is a function like regfilesin that by contract scans all regular files in a directory tree and returns those whose pathname matches a given regexp. Whilst files not marked regular are correctly ignored symlinks to directories are processed. This can lead to an infinite loop. Symlinks to directories must be ignored too. This ensures termination provided hardlinks don't contain cycles. On some OS (MacOS and Linux I think) you cannot create a hard link to a directory, which ensures the graph is acyclic.