feat(dag): basics (put, get)

[daviddias]

Started implementing ipfs-inactive/interface-js-ipfs-core#112 on js-ipfs-api, but there are somethings missing, from ipfs dag cli we have:

» ipfs dag put --help
USAGE
  ipfs dag put <object data> - Add a dag node to ipfs.

SYNOPSIS
  ipfs dag put [--format=<format> | -f] [--input-enc=<input-enc>] [--] <object data>

ARGUMENTS

  <object data> - The object to put

OPTIONS

  -f,        --format string - Format that the object will be added as. Default: cbor.
  --input-enc         string - Format that the input object will be. Default: json.

DESCRIPTION

  'ipfs dag put' accepts input from a file or stdin and parses it
  into an object of the specified format.

It would be great if we could use the multicodec names for the format flag, namely:

• dag-cbor
• dag-pb
• eth-block
• and so on

It will solve a lot of ambiguity. Can we get that @whyrusleeping ?

Another thing, it has no option to pick the hash algorithm to use.

Last note, the --input-enc defaults to json, but if we can use the multicodec of the type, we could send them serialized directly.

[daviddias]

Just realized now that already had started implemented this here and found the same blockers that I have here: #534

Closing in favour of #534