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InfluxDB
Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.
It's not as neat as that unfortunately. You use this to extract different data from the version control history: https://github.com/adamtornhill/code-maat
Then visualize it however. I have some d3 scripts that came with the book that I've modified and you can track down somewhere on github I'm pretty sure. I mostly use those for demoing it to devs unfamiliar with the techniques though, since it looks cool and is immediately obvious what it's for.
For serious use I dump it into sqlite and use a mix of different scripts and techniques to figure it out. It's been kind of a language playground for me over the years so is in a lot of different languages and is "learning code" in most of them. Cleaning them up and sharing is one of those "maybe some day" things though.