Shrinkwrapping with jest takes 30 more seconds due to node_modules

Expected Behaviour

Shrinkwrapping a node project should not take long and should not copy node_modules into build directory because they are ignored by .dockerignore and installed during the build

Current Behaviour

Shrinkwrapping can take up to 30 seconds on a project where most of the function handler's dependencies are devDependencies (e.g. jest)

Are you a GitHub Sponsor (Yes/No?)

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

• Yes
• No

List All Possible Solutions and Workarounds

• Add scripting to save and remove (stash) files/folders that you don't want copied before shrinkwrapping
• Add scripting to re-add removed files after shrinkwrapping

Which Solution Do You Recommend?

I've proposed #888, but maybe there is a way to prefer using .dockerignore files when shrinkwrapping.

Steps to Reproduce (for bugs)

1. Make a new handler using a node template
2. npm i jest --save-dev to that handler
3. faas-cli build --shrinkwrap
4. Add more node_modules to see the copy process take longer

Context

Build time of 60+ seconds for simple projects

Your Environment

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

• Docker version ( Full output from: docker version ):

• Are you using Docker Swarm (FaaS-swarm ) or Kubernetes (FaaS-netes)?

• Operating System and version (e.g. Linux, Windows, MacOS):

• Link to your project or a code example to reproduce issue:

Start with the faas-cli build --shrinkwrap entry point and compare its handling of node_modules with .dockerignore during a Node.js handler build. Reproduce with npm i jest --save-dev, then verify that shrinkwrapping no longer copies unnecessary node_modules content and that build time improves without breaking the generated build directory.