move github stuff to duo-github

[stephenmathieson]

per duojs/duo#116.

this will allow us to abstract all of the api stuff (arguably the most complex part of the codebase), letting this module just handle the important stuff like untarring, caching, installing, etc. it'll also allow us to easily add support for other providers (bitbucket, gitorious, etc.).

public api needs to be decided, but something based on duojs/duo#116 (comment) has my vote:

var pkg = new Package('somebody/something', '0.13.x')
pkg.provider(require('duo-github'))
pkg.token('abcdefg')
pkg.directory('components')
pkg.fetch(function(err){ ... })

var pkg = new Package('someone-else/somerepo', '~0.1')
pkg.provider(require('duo-bitbucket'))
...

var pkg = new Package('someguy/somepackage', '~0.1')
pkg.provider(require('duo-gitorious'))
...

in order to not break back-compat, we could simply add something like:

if (!this.provider()) this.provider(require('duo-github'));

to Package#fetch.

[stephenmathieson]

put together a basic poc here: https://gist.github.com/stephenmathieson/0ac53158570408b0880a

a "provider" (with the above example), exports:

• .resolve: resolve a version number to a tag/branch/whatever
• .tarball: get a tarball url

with this, we're able to pkg.download(url) and extract accordingly.

@matthewmueller @yields thoughts?

[stephenmathieson]

bump

[yields]

looks good to me!

confused about the assert bit though:

/**
 * Require auth.
 */

assert(auth.password,
    'GitHub authentication error: '
  + 'make sure you have ~/.netrc or '
  + 'specify $GH_TOKEN=<token>.'
);

wouldn't this error for everyone who use just bitbucket etc..?
or do we load them dynamically?

otherwise LGTM!