Folders that are not NPM modules but have package.json files are unintentionally pruned

[inukshuk]

As discussed in #844 I've noticed at least one case where a folder (containing a package.json file and nothing else) in a dependency is filtered when packaging an app with the prune option.

Here is a minimal test case:

$ mkdir tmp
$ cd tmp
$ npm init
$ npm i electron electron-packager --save-dev
$ npm i redux-saga
$ $(npm bin)/electron-packager . test --platform=linux

And then:

$ ls -l node_modules/redux-saga/effects/package.json
$ ls -l test-linux-x64/resources/app/node_modules/redux-saga/

And note that the effects folder is missing.

EDIT:

I should add that this does not happen in 11.x.

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[malept]

It's because of this line:

https://github.com/electron-userland/electron-packager/blob/b3c610cd13de72b9b0f22b72c99fb73aa5b53bdb/prune.js#L61

That line needs to be changed so that the check basename(dirname(pathToCheck)) == 'node_modules' is added, along with a regression test.

[malept]

Fix in #847.