Support --target installations with pip freeze

[lkollar]

What's the problem this feature will solve?

List all dependencies with pip freeze which have been installed into an arbitrary directory with pip install --target.

Describe the solution you'd like

pip freeze should have a --target option and take a path to an installation path to work out the installed dependencies in that directory. It should probably also honour the --local flag and skip globally installed packages if specified, just like with virtualenvs, or implicitly disable global site altogether.

I would like to install an application's dependencies into a target directory and then generate a requirements.txt based on the installed packages. At the moment I can only do this if I install the dependencies with --user, inside a virtualenv or by globally installing them.

Alternative Solutions

As far as I know there is no alternative solution to resolve the transitive dependencies and generate a requirements.txt based on a target installation directory.

Additional context