Ignore --raw-leaves when data fits in one block

[achingbrain]

Following on from ipfs-inactive/js-ipfs-unixfs-importer#44 (comment)

If we are importing a file, the returned CID should resolve to a DAG that represents a UnixFS entry. That entry should allow for metadata such as modes, mtimes, etc.

If the --raw-leaves flag has been set, and the data fits in one block, the --raw-leaves flag should be ignored and the data inlined* into the root dag-pb node.

Current behaviour is to return a CID that resolves to a raw node, eg a buffer - this cannot have metadata set on it.

js-IPFS has implemented the change to only output UnixFS things from an import, this issue is to track the go-IPFS version.

cc: @Stebalien @hsanjuan

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* = js-ipfs-unixfs-importer has a reduceSingleLeafToSelf option which allows the user to control whether or not to inline the file data into the root dag-pb node, it's not currently exposed by the ipfs.add command though doing that might be something to entertain. Maybe with a shorter name..

[Stebalien]

This change was never agreed on. Raw leaves are still valid files, they just can't carry metadata. If there's no metadata, there's no reason not to save some space and use a raw leaf.

[achingbrain]

Ah, I think I misread your comment then.

For now, I'd ignore raw leaves when we have metadata and everything fits into a single file.

I guess the distinction is to only do this when we have metadata, not all the time.

[Stebalien]

Yeah, I know it's just a few bytes, but I'd like to be as efficient as possible.

(and, as usual, I'd like to avoid changing hashes unless we have a pressing reason to do so)

[achingbrain]

Ok, this can probably be closed then as the work will be done as part of #6920 which will need to pass the interface and interop tests to be considered done, which include tests for this case so it won't be missed.