add filename filter to modify path and filename

Author: lcxfs1991

README.md

@@ -48,6 +48,15 @@ new ExtractTextPlugin([id: string], filename: string, [options])
 * `options`
   * `allChunks` extract from all additional chunks too (by default it extracts only from the initial chunk(s))
   * `disable` disables the plugin
+  * `filenamefilter` function to modify path and filename before files are emitted
+    ```
+    {
+      filenamefilter: function(filename) {
+        // modify filename
+        return filename;
+      }
+    }
+    ```
 
 The `ExtractTextPlugin` generates an output file per entry, so you must use `[name]`, `[id]` or `[contenthash]` when using multiple entries.
 

index.js

@@ -302,6 +302,7 @@ ExtractTextPlugin.prototype.apply = function(compiler) {
 					}).replace(/\[(?:(\w+):)?contenthash(?::([a-z]+\d*))?(?::(\d+))?\]/ig, function() {
 						return loaderUtils.getHashDigest(source.source(), arguments[1], arguments[2], parseInt(arguments[3], 10));
 					});
+					file = (options.filenamefilter) ? options.filenamefilter(file) : file;
 					compilation.assets[file] = source;
 					chunk.files.push(file);
 				}