Allow changing request.path_info in a before filter that has a pattern.

Fixes #114.

lib/sinatra/base.rb

@@ -28,6 +28,18 @@ def secure?
     else
       alias secure? ssl?
     end
+
+    def route
+      @route ||= begin
+        path = Rack::Utils.unescape(path_info)
+        path.empty? ? "/" : path
+      end
+    end
+
+    def path_info=(value)
+      @route = nil
+      super
+    end
   end
 
   # The response object. See Rack::Response and Rack::ResponseHelpers for
@@ -635,11 +647,7 @@ def route_eval(&block)
     # Returns pass block.
     def process_route(pattern, keys, conditions)
       @original_params ||= @params
-      @path ||= begin
-        path = unescape(@request.path_info)
-        path.empty? ? "/" : path
-      end
-      if match = pattern.match(@path)
+      if match = pattern.match(@request.route)
         values = match.captures.to_a
         params =
           if keys.any?

test/filter_test.rb

@@ -255,6 +255,16 @@ class AfterFilterTest < Test::Unit::TestCase
     assert ran_filter
   end
 
+  it 'changes to path_info from a pattern matching before filter are respoected when routing' do
+    mock_app do
+      before('/foo') { request.path_info = '/bar' }
+      get('/bar') { 'blah' }
+    end
+    get '/foo'
+    assert ok?
+    assert_equal 'blah', body
+  end
+
   it 'generates block arguments from route pattern' do
     subpath = nil
     mock_app do