You used the egg files install procedure.
This procedure supports installing over `git`, `git+http`, `git+https`, `git+ssh`, `git+git` and `git+file`. Some of these are mentioned.

It's good you can use branches, tags, or hashes to install. 

@Steve_K noted it can be slow to install with "git+" and proposed installing via zip file:

    pip install https://github.com/user/repository/archive/branch.zip

Alternatively, I suggest you may install using the `.whl` file if this exists.

    pip install https://github.com/user/repository/archive/branch.whl

It's pretty new format, newer than egg files. It requires wheel and setuptools>=0.8 packages. You can find more in [here](https://pip.pypa.io/en/stable/cli/pip_wheel/).