Add clarifiication on uncle headers

[acolytec3]

Reverts a previous accidental commit to master and then adds clarifying comment defining uncle headers using the devp2p definition for list_of_uncle_headers found here

[carver]

Using devp2p as the reference is not wrong, but also not helpful, maybe? It's really the yellow paper spec that defines it. That format is consensus-relevant, because the uncles hash found in the block header is the hash of rlp.encode(list_of_uncle_headers). That's the primary reason for the choice. I would have a hard time using "devp2p did it this way" as a primary justification for any of our design choices :P

[carver]

The attempt to describe the rationale is here: https://github.com/ethereum/portal-network-specs/blob/e807eb09d2859016e25b976f082735d3aceceb8e/history-network.md#encoding-content-values-for-validation

[acolytec3]

Ah, gotcha, sorry. I remember that in your PR and I'm good with it. I just wanted to explain what list_of_uncle_headers actually was since it's not clearly defined that it's an array of byte arrays where each byte array is the raw bytes representation of the uncle header.

[acolytec3]

I revised my reference to point to the yellow paper and then further define in hopefully clear language how the uncles should be represented.

[carver]

Cool looks good, thanks for adding!

[kdeme]

I think you rather need to say here that it is an RLP encoded list of block headers (from the uncle blocks) that results in a byte string/array.

E.g.:

Suggested change

	Note 2: The `list_of_uncle_headers` refers to the list of uncle headers [defined in the Ethereum yellow paper](https://github.com/ethereum/yellowpaper/blob/30782852fef61f61a247dafbdad814ae7e00fb39/Paper.tex#L399) and is represented as an array of byte arrays where each byte array is the raw bytes representing an uncle header.
	Note 2: The `list_of_uncle_headers` refers to the list of uncle headers [defined in the Ethereum yellow paper](https://github.com/ethereum/yellowpaper/blob/30782852fef61f61a247dafbdad814ae7e00fb39/Paper.tex#L399) and is represented RLP encoded list of block headers, where each block header is the header from an uncle block.

Also, I think a bit more relevant yellow paper link is this line: https://github.com/ethereum/yellowpaper/blob/30782852fef61f61a247dafbdad814ae7e00fb39/Paper.tex#L414 ?

[acolytec3]

I'd be hesitant to say it's an RLP encoded list since that's kind of what the larger content: rlp(list_of_uncle_headers) already says and I'm talking specifically about what's inside the parentheses. I wouldn't want implementers to think we mean our actual code should be rlp.encode(rlp.encode(list_of_uncle_headers)). Otherwise, I'm good with the above.

[kdeme]

Right, forgot about that. Then I'd suggest dropping everything from the and onwards. I mostly wanted to point out that the byte array wording is not really correct.

[acolytec3]

I went with @carver's suggestion. Any last comments before we merge this?

[pipermerriam]

What should happen with this PR?