Pip currently relies on setuptools to perform a setup.py develop install of a package for "editable" installs. This invocation of develop has implicit dependencies on other behaviors such as setup_requires and the old egg-info metadata format.

Setuptools should support generation of more modern metadata formats (dist-info) natively such that tools like pip can create editable installs without invoking legacy behavior.

This functionality doesn't necessarily need to be embedded with setuptools.