supercedes #32642

• FileBasedSource will report every read-in file if number of file <= 100

• FileBasedSource will report every unique directory (one level up) if number of file > 100 but number of unique directory <= 100

• FileBasedSource will report bucket otherwise

• ReadAll will report every file if number of file <= 100

• ReadAll will report bucket otherwise

• FileBasedSink will report every write-to file if shards <= 100

• FileBasedSink (for each destination) will report single directory to write if number of file > 100

In contrast to read, we are able to report single directory because shards are in the same directory.

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