feat(build/serve): export build/serve command and allow them to take config argument (chainable webpack config)

[nklayman]

Solves #1551 by changing the build command to export itself. It can then be imported and ran with a custom config that will be used instead of api.resolveChainableWebpackConfig(). This allows plugins to modify the webpack config only if their build command is run, not for normal builds.

Edit: Now does same process for the serve command.

[nklayman]

Make sure to hide whitespace changes in the diff viewer. Indentation is updated, so it looks like there are more changes.

[nklayman]

For some reason that I can not find, HMR is broken in these cases:

• serve function is imported and called from a plugin
• serve function is called using service.run('serve') (assuming service = new Service(api.resolve('.')))

Yet it still works when:

• serve function is imported and called from a plugin, but only if calling package is linked with yarn link
• called with api.service.run('serve') from a plugin
• called with vue-cli-service serve

[nklayman]

Another method of implementing this feature would be to allow service.run() to take a 4th argument. That argument would be an array of arguments that will be passed to the command the service calls. This would likely fix the HMR issue (and other related ones) and make it easier to add this feature to other plugins. I can create a PR for this method if it is preferred.

[Akryum]

Another method of implementing this feature would be to allow service.run() to take a 4th argument.

Worth a try.

[nklayman]

@Akryum I created a branch with service.run taking a 4th argument: https://github.com/nklayman/vue-cli/tree/service-run-4th-arg

[nklayman]

If that works I can create a PR for that instead.

[nklayman]

Closing as I found an alternative and lack of interest.