legs subscriber must allow datatrasfer to be optionally set

[masih]

Otherwise, a lib2p host with go-legs subscriber cannot start a graphsync server, since registration of stream handler for graphsync server is singular.

It seems limiting to require users of go-legs to not start up a graphsync server if they are running a go-legs subscriber.

Consider adding the option back which was removed here.

Consider alternative approaches to guaranteeing the correctness of blockhook mechanism.

[masih]

Changing that option to take both datatransfer.Manager and graphsync.GraphExchange should be sufficient to allow both registration of block hook at root and instantiate if not set.

[willscott]

or we can add it back on just on the publisher side, right?

[masih]

It was never removed from the publisher side.

[MarcoPolo]

Done in #96