Implement the `jsipfs ls` command

[daviddias]

Following: https://github.com/ipfs/js-ipfs/pull/925/files

We want to support the same command that go-ipfs supports: jsipfs ls.

From go-ipfs:

» ipfs ls --help
USAGE
  ipfs ls <ipfs-path>... - List directory contents for Unix filesystem objects.

SYNOPSIS
  ipfs ls [--headers | -v] [--resolve-type=false] [--] <ipfs-path>...

ARGUMENTS

  <ipfs-path>... - The path to the IPFS object(s) to list links from.

OPTIONS

  -v,           --headers bool - Print table headers (Hash, Size, Name). Default: false.
  --resolve-type          bool - Resolve linked objects to find out their types. Default: true.

DESCRIPTION

  Displays the contents of an IPFS or IPNS object(s) at the given path, with
  the following format:

    <link base58 hash> <link size in bytes> <link name>

  The JSON output contains type information.

[rasmuserik]

I will probably take a look at this next week.

[rasmuserik]

I am starting to look at this now :)

Apparently, at first look, it seems like
directories are currently stored using
using the old Protocol Buffer format,
and not CBOR encoded IPLD?

Are we still only using the (legacy?) protocol buffers,
or should we begin to handle files/directories in IPLD?

---

(Adding a directory yields a block which definitely looks like a protocol buffer, and not CBOR.
I found an example of what a directory in IPLD looks like, but the actual spec for files / unixfs is empty..)

[daviddias]

@rasmuserik dag-pb is not legacy, it is just one of the many formats that IPLD supports. unixfs-engine uses dag-pb and will continue to :)

[rasmuserik]

nice, thanks, that makes things a lot more clear :)
(I thought they were legacy due to this part of the IPLD specs)

[daviddias]

Oh, thanks. We need to review all IPLD specs, added a note to the top of that one to make sure we don't misinform anyone else. Thanks for catching that :)

[rasmuserik]

I've added a pull request #940 which implements the basic functionality, - in hindsight it might be not be the right approach, - but you can choose whether to merge it. (I got to know some parts of IPFS better and I will be looking at other aspects next).