title: Upgrade package without upgrading dependencies using pip?
body: <p>I'm using pip and virtualenv for my python application. I would like to upgrade to a new version of the application without touching the dependencies. When I use <code>pip install -U</code>, it tries to upgrade all the packages, and even uninstalls and re-installs the same version of a dependency package when there isn't a new version available. </p>
  
  <p>I also tried <code>pip install -U --no-deps</code> but that seems equivalent to a regular install instead of an upgrade. Is there a combination of flags that will do what I want?</p>