[technical debt] Decouple MFS from UnixFS

[schomatis]

Checklist

• This is a bug report, not a question. Ask questions on discuss.ipfs.io.
• I have searched on the issue tracker for my bug.
• I am running the latest go-ipfs version or have an issue updating.

Installation method

built from source

Version

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Config

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Description

The general theme of this issue is:

• UnixFS should impelement the File System part of the stack, i.e., mapping local filesystem files, directories, links, etc. to IPFS/IPLD DAGs.
• MFS should only implement the mutable layer of this filesystem DAG (i.e., MFS only adds the M to the FS).

The concrete part of this issue, local to the go-ipfs implementation, is to remove the MFS from the ipfs add command, limiting it only to the ipfs files one. Achieving this will point us in the right direction regarding the general theme above.

More specifically and as a starting point, we should remove the MFS root form the the Adder structure. This is not the permanent MFS root used in the ipfs files command (stored in the repo) but just an ephemeral directory needed to support basic FS operations resulting from the unwanted coupling of UnixFS/MFS.