How do I use 'security set-keychain-settings' to prevent locking? The command line tool security set-keychain-settings provides options for 


locking when the system sleeps (-l) and
locking after a timeout (-u)


but does not seem to provide any options for reversing these settings? 

How to I use  security set-keychain-settings to disable these options?
If you run security set-keychain-settings without anything else it will turn off both "Lock when sleeping" and "Lock after  minutes of inactivity" for the 'login' Keychain. It will also set the default number of minutes back to 5.

From there you can turn on whatever settings you want.