Python / pip, how do I install a specific version of a git repository from github (what is the correct url)?

Specify the branch, commit hash, or tag name after an @ at the end of the url:

pip install git+https://github.com/django/[email protected]

This will install the version tagged with 1.7b3.

Reference: https://pip.pypa.io/en/latest/cli/pip_install/