Restarting a failed poudriere session

There's an option to 
SAVE_WRKDIR=yes
in /usr/local/etc/poudriere.conf

What is its intended use? In particular,
can it be used to pick up a failed build
close to the point where it stopped?

There's no obvious reference to SAVE_WRKDIR
in the man page and a web search came up
empty in terms of what it's good for.

Thanks for reading,

bob prohaska