OUTDATED - Shares the same `ssh-agent` among multiple Cygwin terminals. Source: http://superuser.com/a/141241

sagent.sh

# THERE IS NOW A BETTER WAY TO DO THIS - SEE wsl-ssh-pageant

function sshagent_findsockets {
    find /tmp -uid $(id -u) -type s -name agent.\* 2>/dev/null
}
 
function sshagent_testsocket {
    if [ ! -x "$(which ssh-add)" ] ; then
        echo "ssh-add is not available; agent testing aborted"
        return 1
    fi
 
    if [ X"$1" != X ] ; then
        export SSH_AUTH_SOCK=$1
    fi
 
    if [ X"$SSH_AUTH_SOCK" = X ] ; then
        return 2
    fi
 
    if [ -S $SSH_AUTH_SOCK ] ; then
        ssh-add -l > /dev/null
        if [ $? = 2 ] ; then
            echo "Socket $SSH_AUTH_SOCK is dead!  Deleting!"
            rm -f $SSH_AUTH_SOCK
            return 4
        elif [ $? = 1 ] ; then
            echo "Socket $SSH_AUTH_SOCK is empty!"
            return 5
        else
            echo "Found ssh-agent $SSH_AUTH_SOCK"
            return 0
        fi
    else
        echo "$SSH_AUTH_SOCK is not a socket!"
        return 3
    fi
}
 
function sshagent_init {
    # ssh agent sockets can be attached to a ssh daemon process or an
    # ssh-agent process.
 
    AGENTFOUND=0
    workingsocket=""
 
    # Attempt to find and use the ssh-agent in the current environment
    if sshagent_testsocket ; then AGENTFOUND=1 ; fi
 
    # If there is no agent in the environment, search /tmp for
    # possible agents to reuse before starting a fresh ssh-agent
    # process.
    if [ $AGENTFOUND = 0 ] ; then
        for agentsocket in $(sshagent_findsockets) ; do
            #if [ $AGENTFOUND != 0 ] ; then break ; fi
            if sshagent_testsocket $agentsocket ; then 
                AGENTFOUND=1
                workingsocket=$agentsocket
            fi
        done
    fi
 
    # If at this point we still haven't located an agent, it's time to
    # start a new one
    if [ $AGENTFOUND = 0 ] ; then
        eval `ssh-agent`
    else
        sshagent_testsocket $workingsocket
    fi
 
    # Clean up
    unset AGENTFOUND
    unset agentsocket
    unset workingsocket
 
    # Finally, show what keys are currently in the agent
    ssh-add -l
}
 
alias sagent="sshagent_init"