I want to host my source on bitbucket using git because I obviously get a free private repo and I want to host my app on heroku using the source code from bitbucket.
Chiming in with Stefan - this works perfectly. Here's what I did:
Got really frustrated with the way my WP blog was resetting daily, presenting anyone who navigated to http://blog.example.com with a setup screen, because there was no wp-config.php.
Logged into bitbucket.org.
Linked my bitbucket & github accounts.
Forked my "wp-blog" repo from github, which I had previously linked to my heroku remote.
Cloned into this new fork ("git clone https://myname@bitbucket.org/myname/wp-blog_config.git") .
Added a proper wp-config.php.
Added my heroku remote from within this new fork ("git remote add heroku git@heroku.com:adjective-noun-1234.git")
Committed & deployed to heroku ("git push heroku master:master")