* filer.copy: compute chunk md5 so files get a real ETag
Chunks uploaded by filer.copy had no ETag, so every multi-chunk file got
the md5 of the empty string plus -N. An overwritten file kept its old ETag
and a revalidating client got 304 for changed content.
* filer.copy: store chunks in offset order
Chunks are collected in upload completion order, and the entry ETag
hashes the chunk ETags in stored order. Identical files copied with
concurrent chunk uploads got different ETags, and a file with swapped
equal-sized chunks could keep the old one.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
* filer.copy: test chunk order and chunk md5 on chunked uploads
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---------
Co-authored-by: Chris Lu <chrislusf@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
