Installing Python packages from local file system folder to virtualenv with pip

What about::

pip install --help
...
  -e, --editable <path/url>   Install a project in editable mode (i.e. setuptools
                              "develop mode") from a local project path or a VCS url.

eg, pip install -e /srv/pkg

where /srv/pkg is the top-level directory where ‘setup.py’ can be found.