ipfs get should restore the state to referenced hash and not redo everything

#### Version information:

0.4.13-cc01b7f

#### Type:

Enhancement.

#### Description:

I think it would be great if `ipfs get` would work more like `git checkout`. So if any file got modified or deleted, it would revert those back.

Currently, if I run the same `ipfs get ` command twice in a row, it looks like the whole process is just restarted. I have a huge dataset and this takes quite some time. But sometimes some files in the dataset are temporary changes. Ideally, it should be easy to restore them back to a hashed version. But there is no easy way currently.