Fully support pip options on install

First, thanks for great project 👍 The main thing stopping me from using it is its’ support for pip install. Currently, pipenv is parsing arguments for install and then recreating the pip argument string from them (pip_install).

This allows it to support its own options, but means pip compatibility is limited - e.g. installing in editable mode (-e) or installing from VCS.

It would be possible to support all pip install options by simply forwarding unknown options on pipenv install to pip install (http://click.pocoo.org/5/advanced/#forwarding-unknown-options). This would also mean no development required to support future pip changes. Is that feasible?

[uranusjr]

@benkuhn All pip arguments can be specified as environment variables. You can set PIP_ROOT for --root, for example. Related documentation: https://pip.pypa.io/en/stable/user_guide/#environment-variables

[benkuhn]

Wow, thanks for the tip! Don’t know how I missed that in the Pip docs 😃