poudriere using git+ssh and private key?

Hi,

I'm improving my poudriere setup to get the ports tree via git+ssh.

poudriere ports -c -f "dummypool/poudriere/ports/branchX" -m git+ssh -B "branchX" -p "test" -U ssh://ronald@<githost>/usr/ports

This works from the command line, but it all runs from Jenkins so I don't want interactive passwords for ssh.
How do I pass an ssh private key to the git/ssh invocation?

Regards,
Ronald.