Well, they do explicitly list certain historical features that they don't intend to support, like installation from eggs or editable installs. So they're doing some work to trim the pile while they're there.
``` black @ git+https://github.com/psf/black ```
We also support editable installs for local directories, like you mentioned:
``` black @ ../black ```
The thing we don't support is using _editable_ installs for Git and direct URL dependencies, like:
``` -e git+https://github.com/psf/black ```
In my experience, these are really rare, and we didn't see a reason to support them.