General :: Make Git Use Ssh-add (when Necessary)?

On Linux (CentOS, in case that matters), I'm having a problem with git commands. git can take advantage of keys loaded into the ssh-agent cache, but if the keys aren't loaded, it doesn't seem to take any steps to load them (such as calling ssh-add). I have ~/.ssh/config set up like so:

[Code]....

My system already has ssh-agent set up. I believe it's using an implementation supplied by Gnome [URL] I can manually add my github key with the "ssh-add" command. When I do, I can see that the key is loaded using "git add -l" and the git commands that connect remotely (eg "git remote update") work without prompting for a passphrase. What I still want git commands to do is: By default, if ssh-agent is running and the necessary key is not already loaded, use ssh-add to load the key into ssh-agent. ssh-add appears to need help (via a parameter) if the key file is not one of the default filenames (eg 'id_rsa', 'id_dsa', or 'identity'). This seems backward. I have a mapping from hostname to IdentityFile specified in ~/.ssh/config as shown above. Shouldn't ssh-add be able to use that