DAGService 'recursive' methods

[daviddias]

@whyrusleeping I've a memory of you mentioning that the 'recursive' versions of Add and Remove on the DAGService are deprecated and not used anymore, could you confirm?

https://github.com/ipfs/go-ipfs/blob/master/merkledag/merkledag.go#L71-L89
https://github.com/ipfs/go-ipfs/blob/master/merkledag/merkledag.go#L110-L130

[rht]

Not @whyrusleeping, I think this should be deprecated, but DAG.AddRecursive is still used in the gateway's delete handler, where in this case there should be a pin lock before doing the adding ([bug]).

DAG.RemoveRecursive is not used, but there has been feature requests of manual removal of a specific unpinned dag without having to gc the entire cached blocks (there is a question of whether this should be allowed, or not, much like in the runtime of gc-ed langs).

[rht]

A reason the dag-scale (/ recursive node) operations should not be put into the merkledag spec is that because they have to inter-op with other dag-scale operations (e.g. pinning, gc, or ops in other libs that are using the merkledag).

[whyrusleeping]

confirmed. AddRecursive should be removed wherever possible. We shouldnt rely on the 'node' pointer in the links for anything other than caching. it should not be used to build a tree

[whyrusleeping]

these methods have been removed