Ask HN: Tool to show code age across VCS history

I'm sure there was a Show HN last year for a tool that generates a stacked line graph of the amount of code that has been churned over time. The X axis is time, and the Y is lines of code, and each layer in the stacked graph neatly shows how much original code remains in the code base, and how much has been rewritten. I think its repo shows example graphs for big projects including the Linux kernel.

I've searched for every relevant keyword I can think of but cannot find this tool again. Does anyone also remember it and have a link to it?