Add support for using git tokens in python dependencies

My actions before raising this issue

• Followed the troubleshooting guide
• Read/searched the docs
• Searched past issues

Why do you need this?

PIP has a feature to use a git repo directly as a dependency. Since python doesn't need to be compiled before running it, this allows you to add dependencies, without having to post the code to a library repository like PyPi. In order to use a private repo, you can define the repository in the following way:

git+https://${GITHUB_TOKEN}@github.com/user/project.git@{version}

Here GITHUB_TOKEN is read as an environment variable. In order to use this functionality, I need the ability to specify an environment variable in such a way that it doesn't end up inside the final container (as this would be a security vulnerability).

Expected Behaviour

• GIT_TOKEN can be supplied as a build argument
• this GIT_TOKEN is made available as an environment variable while pip install is running
• the GIT_TOKEN is not made available in the final image

Current Behaviour

To my knowledge, the current python3 template doesn't support providing this GIT_TOKEN.

Are you a GitHub Sponsor (Yes/No?)

Check at: https://github.com/sponsors/openfaas

• Yes
• No

List All Possible Solutions and Workarounds

• you could install the git repo as a submodule, but that feels janky and doesn't handle transitive dependencies
• you can create a private python module repo, but you need to setup some kind of infrastructure, like a nexus server. This request would allow you to completely bypass that. Also, to be able to connect to such a private repo you'd have to configure a token or other kind of auth anyway, so that solution wouldn't have any benefits compared to the github repo solution.

Which Solution Do You Recommend?

Due to the reasons I explained above, I would prefer the ability to use a private git repo in my requirements.txt directly, which requires the GIT_TOKEN env var to be available.

Context

I am a software engineer that runs a local k8s cluster for hobby projects. This cluster also uses OpenFaaS. I am now working on a project where I am using python functions. A lot of these functions share some common code that I now want to separate out into a library, without having to setup too much extra infrastructure.

Your Environment

• FaaS-CLI version ( Full output from: faas-cli version ): 0.13.9

• Docker version docker version (e.g. Docker 17.0.05 ): 20.10.14

• Are you using OpenFaaS on Kubernetes or faasd? On Kubernetes

• Operating System and version (e.g. Linux, Windows, MacOS): Windows + WSL host, ubuntu k8s vm's.