The problem:
Git asks you for your password, when it should just accept your SSH key.
$ git push origin master
Password for 'https://github@github.com':
The solution:
1) First, read the github documentation to ensure your SSH keys are set up correctly
2) Then add this to your ~/.ssh/config:
Host github github.com
Hostname github.com
User git
IdentityFile ~/.ssh/github/id_rsa
3) Finally, clone using ssh instead of https:
git clone https://github.com/username/project-name.git # wrong
git clone git@github.com:username/project-name.git # right
4) Push should now work as expected