Simplest form file uploader.
It just saves uploaded file from HTML form to the new file on the disk.
Also it calculates BLAKE2s checksum, replying with it in the answer.
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+You can upload files with curl:
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+ curl -F fileupload=@somedata.tar.gpg http://localhost:8086/upload/
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+You can verify integrity locally:
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+ b2sum -a blake2s somedata.tar.gpg