sensible defaults for github release

[jasonkarns]

Presently, the github release step requires environment variables with username/password/token.

Git already has a mechanism for accessing this information: .gitconfig.

I submit that grunt-release should get the username/token from git config github.user and git config github.token respectively.

Further, the upstream branch that is used as the push target can be taken from git. It shouldn't need duplicated in the gruntfile:

git rev-parse --symbolic-full-name --abbrev-ref @{upstream}

[geddski]

@jasonkarns not a bad idea, so long as people put it in .git/config and not .gitconfig which would be part of the repo. ENV vars are pretty common for this sort of thing though, so I'd be open to supporting both. You interested in submitting a PR for this?

As for the push target, it just executes a git push, relying on the info in .git/config for which remote the branch is tracking.