core: Add the default server URL

lib/vagrant/shared_helpers.rb

@@ -1,6 +1,13 @@
 require "pathname"
 
 module Vagrant
+  # This is the default endpoint of the Vagrant Cloud in
+  # use. API calls will be made to this for various functions
+  # of Vagrant that may require remote access.
+  #
+  # @return [String]
+  DEFAULT_SERVER_URL = "http://www.vagrantcloud.com"
+
   # This returns whether or not 3rd party plugins should be loaded.
   #
   # @return [Boolean]
@@ -12,8 +19,7 @@ module Vagrant
   #
   # @return [String]
   def self.server_url
-    # TODO: default
-    ENV["VAGRANT_SERVER_URL"]
+    ENV["VAGRANT_SERVER_URL"] || DEFAULT_SERVER_URL
   end
 
   # The source root is the path to the root directory of the Vagrant source.

test/unit/vagrant/shared_helpers_test.rb

@@ -23,6 +23,13 @@ describe Vagrant do
   end
 
   describe "#server_url" do
+    it "defaults to the default value" do
+      with_temp_env("VAGRANT_SERVER_URL" => nil) do
+        expect(subject.server_url).to eq(
+          Vagrant::DEFAULT_SERVER_URL)
+      end
+    end
+
     it "is the VAGRANT_SERVER_URL value" do
       with_temp_env("VAGRANT_SERVER_URL" => "foo") do
         expect(subject.server_url).to eq("foo")