Environment

• pip version: master branch, today
• Python version: 3.8 (probably irrelevant)
• OS: linux (probably irrelevant)

Description

Consider the followingrequirements.txt:

-e git+https://github.com/PyPA/packaging@master#egg=packaging

When we runpip wheel -r requirements.txt --wheel-dir=wheelhouse, we now obtainpackaging-20.5.dev0.zip in thewheelhouse directory, in addition to the expected whl files.

Expected behavior

Only wheels should be generated to the wheel-dir directory.

Analysis

This issue probably originates in#8843 aroundhere although I'm not entirely sure yet.