Remove `IsDir` from `ipfs object`

[jbenet]

currently ipfs object has an IsDir portion:

> ipfs object get QmWNj1pTSjbauDHpdyg5HQ26vYcNWnubg1JehmwAE9NnU9
{
  "Links": [
    {
      "Name": "",
      "Hash": "QmPHPs1P3JaWi53q5qqiNauPhiTqa3S1mbszcVPHKGNWRh",
      "Size": 262158,
      "IsDir": false
    },
    {
      "Name": "",
      "Hash": "QmPCuqUTNb21VDqtp5b8VsNzKEMtUsZCCVsEUBrjhERRSR",
      "Size": 262158,
      "IsDir": false
    },
    {
      "Name": "",
      "Hash": "QmS7zrNSHEt5GpcaKrwdbnv1nckBreUxWnLaV4qivjaNr3",
      "Size": 262158,
      "IsDir": false
    },
    {
      "Name": "",
      "Hash": "QmQQhY1syuqo9Sq6wLFAupHBEeqfB8jNnzYUSgZGARJrYa",
      "Size": 76151,
      "IsDir": false
    }
  ],
  "Data": "\u0008\u0002\u0018��4 ��\u0010 ��\u0010 ��\u0010 ��\u0004"
}

ipfs object is a plumbing command for the merkledag. it must not be aware of (or make assumptions about) datastructures on top, like unixfs. IsDir is unixfs specific. An ipfs unix (or maybe ipfs files) command is planned that will be unixfs specific. IsDir this belongs there, not here.

Sorry @cryptix -- this is my fault for doing lousy CR :( -- i should've explained this then.

[cryptix]

I only added the IsDir field to the Link type in core/commands because it was needed to implement the trailing slash portion of #833. I didn't see a better way for transferring this information from the commands Run() to the Marshalers, especially in the case where Run() executes on the daemon, fetching this information on the client again seemed impractical. If you can show me a better Solution, i'd be happy to fix it.

[jbenet]

Ah, this is tricky. the trailing slash is only on ls, correct? Also, this means that ls is now pulling out the objects themselves to check their type, right? this makes ls more expensive. maybe unixfs should include the type of each link in the Dir entries

[cryptix]

The trailing slash is only on ls, correct?

Effectivly, yes. The changed mashalLinks() function is also used by object stat but there, the additional data isn't fetched, so IsDir is always false. (A quick fix might be to add json:",omitempty")

Also, this means that ls is now pulling out the objects themselves to check their type, right?

Indeed.

maybe unixfs should include the type of each link in the Dir entries

SGTM 😄

[jbenet]

we can just make object and ls use different functions. ls can use its own, with the extra type information.

[cryptix]

fixed by 1f1f9f9