Heroku tracking branch.txt

Assuming you have remote branch called heroku/master, start by creating a local tracking branch 
called heroku.

> git checkout -b heroku -t heroku/master

This will checkout the last revision you deployed to Heroku. 

Now tell git to push the heroku branch to heroku/master

> git config remote.heroku.push heroku:master

You can then make changes on this branch independently of your master 
and when you're ready to deploy to heroku just do this on your local
heroku branch

> git commit -m "Some minor bug fixing"
> git push heroku heroku:master
... Will deploy ...

You can work on features on master:

> git checkout master
> # hack away
> git commit -a -m "My awesome new feature"

To deploy to Heroku

> git checkout heroku
> git merge master
> git push heroku heroku:master

You can use the same technique to have multiple heroku apps for the one codebase,
e.g. a staging and production version.