ipfs config command with git-style option value getters and setters

[dborzov]

Hi there! i wanted to add something small and simple and attempted to make the "ipfs config" command. The idea was to follow git's command line syntax style.

So now we can get specific config's key values with:

        $ipfs config datastore.path
        ~/.go-ipfs/datastore

And assign new values to the keys with:

        $ipfs config datastore.path ~/.go-ipfs/datastore

Plus, in the style similar to:

       git config --global --edit

we can open the config file in the default editor(as taken from $EDITOR environment variable):

       ipfs config edit

One thing to address in the future is that the config keys here are simply read (or assigned) from config's JSON, and just ignore the actual go-ipfs/config structures.
The other one is to add support for custom config file's path.

I would very much appreciate any feedback. Thanks!

[jbenet]

This is great, and totally needed. Thanks! I'll CR shortly-- i'll probably have some comments.

One comment is that, right now, the main codebase is progressing in the dht branch. We can merge later, but might be annoying (thanks to my inconsistent go fmt).

Another comment is that i implemented something similar we can draw from in https://github.com/jbenet/data/blob/master/data_config.go months ago. It probably sucks (and uses yaml), but putting it here for reference.

[dborzov]

Merging this PR into dht seems to be smooth enough. I pulled the dht branch and git cherry-picked the request's commit and it is all ff and fine.

[whyrusleeping]

can you resubmit the pull request against the dht branch then? (not sure if github allows you to change the target branch on the fly)

[whyrusleeping]

The more idiomatic go way of doing this would be to just open the file os.Open and then use json.NewDecoder to do the decoding.

fi,err := os.Open(filename)
if err != nil {//whatever}
dec := json.NewDecoder(fi)
var cfg map[string]interface{}
err := dec.Decode(&cfg)
if err != nil {//whatever}

(obviously written cleaner than my chicken scratch)

[dborzov]

I can rewrite it using json.Decoder, but I don't really see that much of a difference.
Could you please comment on why this way is preferable / more idiomatic?

[whyrusleeping]

@jmoiron does a good job explaining it in one of his articles: http://jmoiron.net/blog/crossing-streams-a-love-letter-to-ioreader/

[jbenet]

That's a good post!

@dborzov I can rewrite it-- there's a few more stylistic things i'll fix that don't want to annoy with.

[dborzov]

Thanks for the link, that article makes good sense to me.

[jbenet]

Awesome, merged manually in 4b1bae8...639d196 (onto master), thanks!

[jbenet]

Note the new help message, for some of the changes I made.

> ipfs config
ipfs config [<key>] [<value>] - Get/Set ipfs config values.

    ipfs config <key>          - Get value of <key>
    ipfs config <key> <value>  - Set value of <key> to <value>
    ipfs config --show         - Show config file
    ipfs config --edit         - Edit config file in $EDITOR

Examples:

  Get the value of the 'datastore.path' key:

      ipfs config datastore.path

  Set the value of the 'datastore.path' key:

      ipfs config datastore.path ~/.go-ipfs/datastore

[dborzov]

Great, the rewrite looks very nice, thanks!

There is a related thing I wanted to ask about.

There are hooks all over the place to pass the custom path to config file with a flag. There is also a TODO comment on that at cmd/ipfs/ipfs.go:69. Would it be easier to just read it off the ENV variable? Something like $IPFS_CONFIG? Then you can just achieve the same thing within the same line of shell command:

         IPFS_CONFIG=/my/path ipfs blah-blah

[jbenet]

Hm, yeah, we could use an env variable. Am on the fence about that-- there are many programs on either camp. shrug I don't care much either way.