npm file+pack protocol feature

This is an idea for RFC https://github.com/npm/rfcs/pull/150

Trying it locally

After cloning the project, do:

npm install
npm link

Then you can cd into tests/npm-filepack/root-package and run:

npm-filepack
npm start

Or cd into tests/filepack/root-package and run:

filepack
npm start

This will install two local dependencies test-package-a and test-package-b, where test-package-b also depends on test-package-a while also requiring typescript compiling, which will be executed before packing and linking to root-package

npm-filepack vs filepack?

npm-filepack is meant to be like a "built-in" behavior of npm, if npm allowed file+pack: protocol.

filepack is an external tool (very much like lerna or others), which will use filepackDependencies and filepackDevDependencies from package.json to resolve tarballs. This produces a side effect on package.json, adding tarball entries in dependencies and devDependencies respectively!

Once filepack has been run once:

• it's not necessary to run it again until we want to rebuild tarballs
• npm install can be run normally, and all npm commands will be working :tada: