If torrent is not private, leave private flag unset

[feross]

If torrent is not private, leave private flag unset. This ensures that the torrent info hash will match the result generated by other tools, including webtorrent-cli.

Fixes: webtorrent/webtorrent-hybrid#79

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More info:

WebTorrent Desktop uses the result of the "Private" checkbox at torrent creation time to set the torrent's private flag to true or false. Unfortunately, there's an issue with the way this private flag spec was designed. There are actually 3 possible values for the private flag:

• private: true
• private: false
• not specified (defaults to false)

The problem is that private flag is part of the info section in the .torrent file, which means that each of these three values for private will produce a different info hash.

So, what's happening is that webtorrent-cli and webtorrent-hybrid are not setting private at all, while WebTorrent Desktop is setting it to false.

We should either set it to true or leave it not specified to match what webtorrent-cli, webtorrent-hybrid, and other mainstream torrent clients do.

[DiegoRBaquero]

Makes sense to leave it unset rather than changing the others to setting it to false. It's unneeded info in the torrent tbh.

[codealchemist]

Makes sense and the change is looking good.
Thanks!

[feross]

Thanks for the review!