How do I use GitHub with SSH without having to run ssh-agent?

In order to push/pull from GitHub using SSH, I have to...

$ eval $(ssh-agent -s)
$ ssh-add ~/.ssh/git_id_rsa
$ git push origin master

However, when I push/pull to remote git repositories I host on my own private server, I can skip the whole ssh-agent stuff and simply

$ git push origin master

How do I do the same with GitHub (push/pull without ssh-agent set-up and ssh-add)?

My id_rsa keys do not have passphrases associated with them
I am comfortable with the level of security this provides
I know how to set-up bash aliases for these, and run them on start-up/bash exit, but I would rather not deal with them at all

Solution

You can use config file in .ssh directory of your user in order to configure key for particular server:

# ~/.ssh/config
Host github.com
    IdentityFile ~/.ssh/git_id_rsa