title: Check overall progress made in a git repository
body: <p>There's a git repository which I'd like to "monitor". There's a lot going on in it, new branches, old ones going away either bc merged or abandoned, tags, push -f, GC, so on. I clone it at some point in time and then after a bit of time, I'd like to get an overall picture of things that have happened in the repository. (Obviously, I don't need intermediate stages, just comparing the two DAG snapshots.)</p>
  
  <p>I'm happy to create a new clone and compare it with the previous one if needed, but somehow, I'd like to see some sort of a readable diff of the two DAGs. What'd be a good way to approach this? </p>