Option to restrict churn to a time range

[jamie]

Love this, it's a great UX to this kind of analysis.

I've got a 10+ year old Rails app though, and would love to restrict the churn analysis to a shorter timeframe (something that originally churned but has been stable for a few years isn't worth stressing over) - I was able to just edit the git analyzer to add --since="2 years ago" and get a more smoothed out X axis, but it'd be great if there was a commandline option to tweak instead.