git clone https://github.com/paul-gauthier/aider.git

In the local aider folder, execute:

python -m venv .venv

source .venv/bin/activate   # For macOS/Linux
.venv\\scripts\\activate      # For Windows

Then:

pip install -e .

To upgrade:

pip install --upgrade .

For venv:
.venv\Scripts\python.exe -m pip install --upgrade aider-chat