Comment 1 for bug 1257706

It depends on what you intend to use gpg-agent for. For caching of your passphrase of your gpg private key, I assume you don't need the SSH variables exported. But if you want gpg-agent to use as a ssh-agent too, you need to pass --enable-ssh-support to gpg-agent and export SSH_AUTH_SOCK (the man page only mentions SSH_AUTH_SOCK in the examples).

I use gpg-agent as a ssh-agent too, so I can use my OpenPGP card for SSH authentication. I've attached my ~/.init/gpg-agent.conf (used by upstart user sessions) which starts gpg-agent with --enable-ssh-support and exports SSH_AUTH_SOCK. Put it in your ~/.init/ and upstart will use it instead the one from the package.

I doubt this can be included in the package itself (perhaps as an example for those users who need it) as gpg-agent will then compete with ssh-agent (from the openssh-client package) who sets the SSH_AUTH_SOCK variable and might upset users of ssh-agent. gnome-keyring can also act as a ssh-agent so there are at least three competioners for that variable.