Deprecate input-enc, add input-format, handle graceful upgrade

[rvagg]

Ref: #8415

Here's a proposal for handling a graceful transition for input-enc behaviour for 0.10.0.

Ideally I'd like input-enc to not be shown on the help output but in lieu of that I thought adding a "DEPRECATED" notice might be a good idea.

The behaviour here is:

1. If you supply input-format then use that, ignoring input-enc
2. if you don't supply an input-format or an input-enc then default input-format to dag-json
3. If you don't supply an input-format but do supply an input-enc then map as per current behaviour in https://github.com/ipfs/go-ipfs/blob/master/core/coredag/dagtransl.go - which is essentially accepting input as bytes presumed to be in format codec except in the case of json where we switch to dag-json.

There is some laxity around input-enc that doesn't currently exist - it'll accept any valid codec too and just push that into input-format so it can be used as an alias for input-format in that case (I mainly did this to get the proper error output for a bad value).

This makes https://github.com/ipfs/js-ipfs/blob/870d446f/packages/ipfs-http-client/test/dag.spec.js pass except for the missing cid-version and new default of CIDv1.

So, ipfs dag put --input-enc=raw --format=dag-pb works as per previous versions in that it's going to assume you're giving it bytes of a valid dag-pb block. This would be ipfs dag put --input-format=dag-pb --format=dag-pb in the new style, whereas ipfs dag put --input-format=raw --format=dag-pb is not going to work because you can't just stick a single byte array into a dag-pb codec, that's invalid.

For another example, ipfs dag put --input-enc=raw --format=dag-cbor is going to be the same as ipfs dag put --input-enc=raw --format=dag-cbor, but ipfs dag put --input-format=raw --format=dag-cbor is entirely different and would encode your incoming bytes as a single terminal CBOR with the "byte string" prefix.

[aschmahmann]

closed by the alternatives in #8439 #8440