Add alias feature to rewrite urls

[bbtfr]

Hi guys,
I found sometimes, it's not easy to change the source file / input file of css-loader, e.g.: when we're using sass files in another package (bootstrap-sass), we'll get a lot of complains about Cannot resolve 'file' or 'directory' ....
There are tons of questions on Google about this.
For bootstrap, we may use $icon-font-path or bootstrap-loader, but for other projects, we have nothing.
resolve-url-loader is a solution, but it's based on source-map and makes the compilation much slower.
So what do you think if we rewrite urls in css-loader?

Here's an example to load bootstrap-sass with sass-loader, css-loader & style-loader

// webpack.config.js
// ## Webpack Configuration
var path = require('path');

module.exports = {
  entry: "./src/entry",
  output: {
    filename: 'bundle.js',
    path: path.resolve('./dist')
  },
  module: {
    // ### Loaders
    loaders: [
      { test: /\.js$/, loader: "babel" },
      { test: /\.scss$/, loader: "style!css!sass" },
      { test: /\.(woff|woff2|ttf|eot|svg)$/, loader: "url?limit=10000" }
    ]
  },
  cssLoader: {
    alias: {
      "../fonts/bootstrap": "bootstrap-sass/assets/fonts/bootstrap"
    }
  },
  sassLoader: {
    includePaths: [
      path.resolve("./node_modules/bootstrap-sass/assets/stylesheets")
    ]
  }
};

// stylesheet.scss
@charset "UTF-8";
@import "bootstrap";

cssLoader.alias use the same syntax with resolve.alias, https://webpack.github.io/docs/configuration.html#resolve-alias

[codecov-io]

Codecov Report

Merging #274 into master will increase coverage by 0.11%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master    #274      +/-   ##
=========================================
+ Coverage   98.19%   98.3%   +0.11%     
=========================================
  Files           9      10       +1     
  Lines         332     354      +22     
  Branches       75      79       +4     
=========================================
+ Hits          326     348      +22     
  Misses          6       6

Impacted Files	Coverage Δ
lib/createResolver.js	100% <100%> (ø)
lib/loader.js	100% <100%> (ø)	✅

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[michael-ciniawsky]

Alias is good idea 👍, can you check against webpack 2 / webpack 2 options syntax please?

[joshwiens]

This will need to be updated to 2.x syntax before it's reviewed. With the defaults updates requiring major versions, this would have to be compatible / focused on Webpack > 2.0

[jsf-clabot]

All committers have signed the CLA.

[bebraw]

Can you sign the CLA and document the feature at readme?

[bbtfr]

The code has been rebased, updated to 2.x syntax
The alias resolving functionality has been moved to createResolver.js, so it would be clearer
And the document is also been updated

[michael-ciniawsky]

@bbtfr Thx