p2p: report-peer-id option for listen

[magik6k]

Was suggested on IRC, when set it basically passes QmPeerid\n of connecting peer into listener stream.

(works but needs tests)

[Stebalien]

We should also consider sending a binary peer ID (maybe length-prefixed?, although peer IDs are already prefix-free codes). This may be easier to parse than having to read to a newline and then potentially base58 decode. It also means we can change encoding without breaking things.

However, I haven't thought though this thoroughly.

[magik6k]

Technically they carry the multihash prefix which has length. I can see binary form being useful, but I can't think of any nice way to do this other than 2 separate flags

[Stebalien]

Meh. The current version is quite user friendly.

Any objections @ipfs/go-team?

[whyrusleeping]

Eh, I think that practically, the base58 encoded version will be the most useful. If we make it binary, writing a parser becomes just that much more difficult.

[Stebalien]

A week has gone by, @whyrusleeping has given his blessing, 🚂.