Support yarn

[vladimyr]

This resolves #195 by supporting following scenario:

$ NPM_CHECK_INSTALLER=yarn npm-check

Also if yarn's lockfile has been found it will be used as default package manager 🎉

[vladimyr]

Those build failures are due to node@4 lacking es6 support...

[hacknug]

@dylang any chance this could be reviewed and merged? For some reason, yarn upgrade-interactive isn't as reliable for me as your package 🤷‍♂

[VincentLanglet]

@dylang This would be great

Edit: It seems there is another PR https://github.com/dylang/npm-check/pull/365/files

[dkhunt27]

Merged with #397

[fschoenfeldt]

By the way, by using NPM_CHECK_INSTALLER=yarn npm-check, yarn tries to install via yarn install which doesn't work anymore:

? Choose which packages to update. gatsby-plugin-react-svg@3.0.1, gatsby-plugin-webfonts@2.1.1, lottie-web@5.7.12, babel-plugin-styled-compo
nents@1.13.2, babel-preset-gatsby@1.10.0, gatsby@3.10.2, gatsby-cli@3.10.0, gatsby-image@3.10.0, gatsby-plugin-manifest@3.10.0, gatsby-plugi
n-offline@4.10.0, gatsby-plugin-react-helmet@4.10.0, gatsby-plugin-robots-txt@1.6.8, gatsby-plugin-sharp@3.10.2, gatsby-plugin-styled-compon
ents@4.10.0, gatsby-source-filesystem@3.10.0, gatsby-source-graphql@3.10.0, gatsby-transformer-json@3.10.0, gatsby-transformer-sharp@3.10.0,
 react-intersection-observer@8.32.0, sanitize-html@2.4.0, styled-components@5.3.0

$ yarn install --save gatsby-plugin-react-svg@3.0.1 gatsby-plugin-webfonts@2.1.1 lottie-web@5.7.12 babel-plugin-styled-components@1.13.2 babel-preset-gatsby@1.10.0 gatsby@3.10.2 gatsby-cli@3.10.0 gatsby-image@3.10.0 gatsby-plugin-manifest@3.10.0 gatsby-plugin-offline@4.10.0 gatsby-plugin-react-helmet@4.10.0 gatsby-plugin-robots-txt@1.6.8 gatsby-plugin-sharp@3.10.2 gatsby-plugin-styled-components@4.10.0 gatsby-source-filesystem@3.10.0 gatsby-source-graphql@3.10.0 gatsby-transformer-json@3.10.0 gatsby-transformer-sharp@3.10.0 react-intersection-observer@8.32.0 sanitize-html@2.4.0 styled-components@5.3.0 --color=always
Command failed: yarn install --save gatsby-plugin-react-svg@3.0.1 gatsby-plugin-webfonts@2.1.1 lottie-web@5.7.12 babel-plugin-styled-components@1.13.2 babel-preset-gatsby@1.10.0 gatsby@3.10.2 gatsby-cli@3.10.0 gatsby-image@3.10.0 gatsby-plugin-manifest@3.10.0 gatsby-plugin-offline@4.10.0 gatsby-plugin-react-helmet@4.10.0 gatsby-plugin-robots-txt@1.6.8 gatsby-plugin-sharp@3.10.2 gatsby-plugin-styled-components@4.10.0 gatsby-source-filesystem@3.10.0 gatsby-source-graphql@3.10.0 gatsby-transformer-json@3.10.0 gatsby-transformer-sharp@3.10.0 react-intersection-observer@8.32.0 sanitize-html@2.4.0 styled-components@5.3.0 --color=always
warning ../../package.json: No license field
error `install` has been replaced with `add` to add new dependencies. Run "yarn add gatsby-plugin-react-svg@3.0.1 gatsby-plugin-webfonts@2.1.1 lottie-web@5.7.12 babel-plugin-styled-components@1.13.2 babel-preset-gatsby@1.10.0 gatsby@3.10.2 gatsby-cli@3.10.0 gatsby-image@3.10.0 gatsby-plugin-manifest@3.10.0 gatsby-plugin-offline@4.10.0 gatsby-plugin-react-helmet@4.10.0 gatsby-plugin-robots-txt@1.6.8 gatsby-plugin-sharp@3.10.2 gatsby-plugin-styled-components@4.10.0 gatsby-source-filesystem@3.10.0 gatsby-source-graphql@3.10.0 gatsby-transformer-json@3.10.0 gatsby-transformer-sharp@3.10.0 react-intersection-observer@8.32.0 sanitize-html@2.4.0 styled-components@5.3.0" instead.

For more detail, add `--debug` to the command

For now, I just run the suggested yarn add ... command. 😄