title: How to detect code change frequency?
body: <p>I am working on a program written by several folks with largely varying skill level. There are  files in there that have never changed (and probably never will, as we're afraid to touch them) and others that are changing constantly.</p>
  
  <p>I wonder, are there any tools out there that would look at the entire repo history (<code>git</code>) and produce analysis on how frequently a given file changes? Or package? Or project?</p>
  
  <p>It would be of value to recognize that (for example) we spent 25% of our time working on a set  of packages, which would be indicative or code's fragility, as compared with code that "just works".</p>