Pikpak can accelerate file uploads by leveraging existing content
in its storage (identified by a custom hash called gcid).
Previously, file transfer statistics were incorrect for uploads
without outbound traffic as the input stream remained unchanged.
This commit addresses the issue by:
* Removing unnecessary unwrapping/wrapping of accountings
before/after gcid calculation, leading immediate AccountRead() on buffering.
* Correctly tracking file transfer statistics for uploads
with no incoming/outgoing traffic by marking them as Server Side Copies.
This change ensures correct statistics tracking and improves overall user experience.
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