Created attachment 2396 [details]
IdentityPersist patch

Background:

I want to add an identity to an authentication agent automatically
when I load the identity.  Gnome-keyring has such a feature by using a
modified ssh-agent, but I don't want to run the gnome-keyring's agent
only for this feature.

Specification:

I propose to add two options called IdentityPersist and
IdentityPersistConfirm to accomplish this feature.

IdentityPersist can take a boolean value or a time value like:

    # keep identities forever
    IdentityPersist yes
    # keep identities for 5 minutes
    IdentityPersist 300 

If the value is true or a time, then ssh-agent will try to add an
identity to itself automatically when the identity is being loaded.
If the time value is given, ssh-agent will forget the identity in
seconds the value specified.  The default value is false.

IdentityPersistConfirm can take a boolean value.  If the value is
true, then ssh-agent will confirm to an user that the identity should
be added or not.  The default value is false.

Implementation and test:

I have attached a patch.  It's a tiny change, so you can read the
modification in few minutes.  I have tested on Debian/GNU Linux 7.0.
I have also checked the patch doesn't break a build on Debian/GNu
Linux 7.0 and OpenBSD 5.4.