pip freeze has no fidelity if the source is other than PyPI pkg

[chadmiller]

• Pip version: 8.1.2
• Python version: 3.4.5
• Operating System: linux, fbsd

Description:

I expect "pip freeze" to create a file that can reproduce what "pip install" did. That doesn't happen when the install argument is not a PyPI package name.

What I've run:

$ pip install git+https://github.com/chadmiller/textbot_metapriv.git#egg=textbot_metapriv   # a private package that will never be in PyPI
$ pip freeze |grep bot
textbot-metapriv==1.0

So, pip install -r ... will later fail.

[xavfernandez]

Duplicate of #609