send file name

[notune]

I think it would be a great feature to include the file name as well. (or maybe just the file extension). This would only require a few additional bytes to be sent.

[sz3]

It'd be helpful.

I left it out initially due to (perceived) security risk on my part. I've sort of come around on it though -- I don't think it's too scary to have the file declare what it is, since a troublemaker would be able to do the same sort of things without it anyway:

😈 : just rename 1.123456 to "notavirus.pdf" and open it!

vs just getting the save dialogue for "notavirus.pdf"

There's kind of an inherent trust issue with being able to send the whole file in the bar code regardless, so I'd like to try to communicate that better as I (slowly) add more usability.

[sz3]

Implementation wise, I alluded to it here

another option is to use the "skippable frame" functionality of zstd to attach some metadata to the transfer.

That's probably how I would (hopefully will) do it: make it entirely optional on the receiver's end as to whether to pay attention to the filename, but make sure the sender includes it.

We're already using skippable frames to pad small files up to the fountain (wirehair) block size, so it's not too crazy.