File paths can now be changed by filters.

This commit adds an extension point called "path" to allow the
modification of file paths before they are open.

doc/methods.markdown

@@ -136,6 +136,11 @@ If `ext` is 'post', execute the wrapper on the entire bundle.
 If `ext` is 'pre', call the wrapper function with the bundle object before the
 source is generated.
 
+If `ext` is 'path', execute the wrapper for every `file` before it is open,
+allowing the extension to change it. `fn` gets called as `fn.call(b, file)`
+for the bundle instance `b` and the file path `file`. `fn` should return the
+new path to the file.
+
 If `ext` is an object, pull the extension from `ext.extension` and the wrapper
 function `fn` from `ext.wrapper`. This makes it easy to write plugins like
 [fileify](https://github.com/substack/node-fileify).

lib/wrap.js

@@ -41,6 +41,7 @@ function Wrap (opts) {
 
     this.files = {};
     this.filters = [];
+    this.pathFilters = [];
     this.postFilters = [];
     this.preFilters = [];
     this.aliases = {};
@@ -99,6 +100,9 @@ Wrap.prototype.register = function (ext, fn) {
     else if (ext === 'pre') {
         this.preFilters.push(fn);
     }
+    else if (ext === 'path') {
+        this.pathFilters.push(fn);
+    }
     else if (fn) {
         this.extensions.push(ext);
         this.filters.push(function (body, file) {
@@ -137,6 +141,10 @@ Wrap.prototype.reload = function (file) {
 Wrap.prototype.readFile = function (file) {
     var self = this;
 
+    self.pathFilters.forEach(function (fn) {
+        file = fn.call(self, file);
+    });
+
     var body = fs.readFileSync(file, 'utf8').replace(/^#![^\n]*\n/, '');
 
     self.filters.forEach(function (fn) {