In applyTar, if the driver's ApplyDiff returns an error, the function
returns early without calling io.Copy.
As a consequence, the resources (a goroutine and some buffers holding
the uncompressed image, the digest, etc...) allocated or referenced by
NewInputTarStream above aren't released, as the worker goroutine only
finishes when it finds EOF or a closed pipe.
Signed-off-by: Sergio Lopez <slp@redhat.com>
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