Fix npm@6 warnings about deprecated "prepublish"

[IvanGoncharov]

NPM 6 produces this warning:

npm WARN prepublish-on-install As of npm@5, `prepublish` scripts are deprecated.
npm WARN prepublish-on-install Use `prepare` for build steps and `prepublishOnly` for upload-only.
npm WARN prepublish-on-install See the deprecation note in `npm help scripts` for more information.

Yarn/NPM support new prepublishOnly property:

As of npm@4.0.0, a new event has been introduced, prepare, that preserves this existing behavior. A new event, prepublishOnly has been added as a transitional strategy to allow users to avoid the confusing behavior of existing npm versions and only run on npm publish (for instance, running the tests one last time to ensure they're in good shape).

Currently NPM deploy done using:

graphql-js/.travis.yml

Line 34 in 2eccaad

node_js: '8'

which use NPM 5.

[IvanGoncharov]

@mjmahone Thanks.

[mjmahone]

@IvanGoncharov did my squash-and-merge give you the proper attribution? I want to make sure I'm not rewriting pull-request owners somehow, and that you're getting due credit for anything we pull in! If I did mess things up, I'm sorry and will happily change my merge flow.

Also thank you for this fix!

[IvanGoncharov]

@mjmahone Everything is fine it's look like this:

Plus GitHub counts me as an author so I still have a chance to beat greeenkeeper[bot] one day 😆

[intellix]

Maybe it'd be good to support npm prepare script which can just be a reference to npm build

[IvanGoncharov]

@intellix Why would you need to build dist folder on npm install?
If you want to try master there is a special branch for that:
https://github.com/graphql/graphql-js#want-to-ride-the-bleeding-edge

Or do you need it for something else?

[intellix]

It'd support bleeding edge without requiring a special branch. You could install any branch like: github:graphql/graphql-js#whatever

It won't build a dist upon npm install, it'll just support the above without any consequence or complexities. It's new since npm 5

[IvanGoncharov]

@intellix I wrote a pretty long response but I don't want it to be lost inside merged PR with an unrelated title.
Can you please open an issue for that feature?

[IvanGoncharov]

@intellix Short version: for this to work we need to make npm run build Windows-friendly which is a big problem on its own.

[leebyron]

woohoo!