[boyter]

This is not open source specific but what I do to any code base I am expected to understand and be prouductive with.

I usually start by running cloc and sloccount to get an idea of the metrics of it, languages line of code estimates etc...

I progress to looking at the tests if there are any. They usually give an idea of how the authors expect things to work.

Once I have browsed some of the tests, in particular integration tests I start following how they work through the code. Your IDE of choice will help out here or failing that use ripgrep, ack, the silver searcher, searchcode server (note I run this so I am biased), sourcegraph.

One thing that I have found especially valuable is running something to determine the cyclomatic complexity of the code. Knowing which parts are complex is a good way to determine where you should focus your time.