feat: deprecate confusing baseUrl option, use publicPath instead.

[haoqunjiang]

In most cases we use baseUrl as a way to modify publicPath safely.
The name baseUrl did mislead some people: in some rare cases we want to modify the publicPath of static assets while not influencing the page url (#2788). In that case this option does not indicate the base location of the web page but the application bundle, publicPath would be a better and more common name for it.

(One exception is process.env.BASE_URL, I'm still wondering if we should rename that env variable too).

[IndexXuan]

only change in vue.config.js and the same with baseUrl ?
why not use process.env.PUBLIC_URL like create-react-app ?

[haoqunjiang]

@IndexXuan PUBLIC_URL is not the same as publicPath in webpack config.

[IndexXuan]

@sodatea replace baseUrl as publicPath do the same with before ?
what different with publicPath and PUBLIC_URL in production

[haoqunjiang]

@IndexXuan
publicPath better reflects the actual usage of this option.

PUBLIC_URL is like BASE_URL in this PR. It's meant to be read-only and exposed by Vue CLI rather than the user.
I was thinking about changing the name too.

[IndexXuan]

@sodatea Our product is a service that user upload source code and we build them and publish in CDN and html serve in somewhere. Our CI export PUBLIC_URL so that user not care about that, just use it in build scripts(Vue CLI 3 is vue.config.js#baseUrl before) and CRA user use PUBLIC_URL too.

Change baseUrl to publicPath is safely for us ?

strongly WANT PUBLIC_URL !!!

[haoqunjiang]

Well, in that case, it’s safe to use publicPath, this PR is nothing more than a name change. They work identically underlyingly.

[IndexXuan]

@sodatea this name change break some Vue CLI 3 plugin which use projectOptions#baseUrl, like:
https://github.com/longshihui/vue-cli-plugin-navigator/blob/master/service/index.js#L68

[haoqunjiang]

@IndexXuan Got it. Will fix it in the next patch. (By making publicPath and baseUrl truly interchangable)