Support requirements.txt for template hooks

[michael-todorovic]

Hello,
We'd like to use python hooks, rather than bash as it supports easy sharable libraries. However, I didn't find a way to manage those dependencies.

Could we imagine that cookiecutter runs a pip install -r requirements.txt contained in a template to install required dependencies for the hooks? Or do you prefer to keep this separated from cookiecutter?

We can likely provide a PR for this feat if you're interested in it 😄

Thanks!

[alanverresen]

Cookiecutter currently does not have any built-in functionality to install packages for your hooks, but it is possible to use packages within your hooks. I'm not a core member of this project, but here's my two cents.

Unless there's something that I'm missing, cookiecutter and its hooks are ran on top of your current environment's Python binary/installation, so if you install the needed dependencies before running cookiecutter, you can import them within the hooks. If you need isolation, you can use pipx, venv, etc. to run cookiecutter in a virtual environment with your dependencies installed.

You can also use cookiecutter's hooks to act as a bootstrap for your actual hook scripts:

1. create and activate a virtual environment
2. install the needed dependencies
3. run your actual hook script

If cookiecutter were to add built-in functionality to install a hook's dependencies, I imagine that it would use a virtual environment to execute the hooks in the same way as I described above.