`box.url` can use `file://` URI

lib/vagrant/downloaders/file.rb

@@ -1,4 +1,5 @@
 require 'fileutils'
+require 'uri'
 
 module Vagrant
   module Downloaders
@@ -6,7 +7,8 @@ module Vagrant
     # simply does a file copy.
     class File < Base
       def self.match?(uri)
-        ::File.file?(::File.expand_path(uri))
+        extracted = URI.extract(uri, "file")
+        (extracted && extracted.include?(uri)) || ::File.file?(::File.expand_path(uri))
       end
 
       def download!(source_url, destination_file)

lib/vagrant/downloaders/http.rb

@@ -10,7 +10,7 @@ module Vagrant
     class HTTP < Base
       def self.match?(uri)
         # URI.parse barfs on '<drive letter>:\\files \on\ windows'
-        extracted = URI.extract(uri).first
+        extracted = URI.extract(uri, ['http', 'https']).first
         extracted && extracted.include?(uri)
       end
 

test/unit/vagrant/downloaders/file_test.rb

@@ -37,6 +37,10 @@ describe Vagrant::Downloaders::File do
         ENV["HOME"] = old_home
       end
     end
+
+    it "should match file:// URIs" do
+      described_class.match?("file://#{__FILE__}").should be
+    end
   end
 
   describe "downloading" do

test/unit/vagrant/downloaders/http_test.rb

@@ -11,6 +11,10 @@ describe Vagrant::Downloaders::HTTP do
       described_class.match?("http://foo:bar@google.com/foo.box").should be
       described_class.match?("http://google.com:8500/foo.box").should be
     end
+
+    it "should not match file:// URIs" do
+      described_class.match?("file://#{__FILE__}").should_not be
+    end
   end
 
   describe "downloading" do