title: log all pip commands in a given virtual environment?
body: <p>I'd like to keep a record of all <code>pip</code> commands that were executed in a given virtual environment and of the package versions that got installed/updated/removed. Is there an easy way to do that?</p>
  
  <p>Alternatively, how do I get <code>requirements.txt</code> (including <code>--install-option</code>, etc.) out of my virtual environment state, if that's possible? Presumably, only the immediate dependencies need to be there.</p>