This was a quick project to log temperature as well as humidity at regular intervals for a friends biology project. It logged data via a simple bash script, and turned on and off the lights via a cron job + web interface. The key learnings from this experiment was that the in soil humidity probes do not last that long: they degrade after sitting in humid soil for a few months.
Unfortunately since this project is from a few years ago I don't have the source code anymore. Back then I used to ssh into the Pi and edit code directly on it, without using version control :/