Use the .vagrantrc for plugins!

CHANGELOG.md

@@ -6,8 +6,8 @@
     so that plugins will always _load_ (though they will almost certainly
     not be _functional_ in future versions of Vagrant).
   - Plugins no longer "autoload" by simply gem installing them. This increases
-    Vagrant's initial startup time considerably. To replace this, you can use
-    the `vagrant plugin` interface.
+    Vagrant's initial startup time considerably. To replace this, you must now
+    explicitly require plugins in the `~/.vagrantrc` file.
   - Improve the SSH "ready?" check. [GH-841]
   - Human friendly error if connection times out for HTTP downloads. [GH-849]
   - Detect when the VirtualBox installation is incomplete and error. [GH-846]

lib/vagrant/environment.rb

@@ -15,6 +15,7 @@ module Vagrant
     HOME_SUBDIRS = ["tmp", "boxes", "gems"]
     DEFAULT_VM = :default
     DEFAULT_HOME = "~/.vagrant.d"
+    DEFAULT_RC = "~/.vagrantrc"
 
     # The `cwd` that this environment represents
     attr_reader :cwd
@@ -519,7 +520,15 @@ module Vagrant
       ::Gem.clear_paths
 
       # Load the plugins
-      # XXX: TODO
+      rc_path = File.expand_path(ENV["VAGRANT_RC"] || DEFAULT_RC)
+      if File.file?(rc_path)
+        # We use a `require` here instead of a load so the same file will
+        # only be loaded once.
+        @logger.debug("Loading RC file: #{rc_path}")
+        require rc_path
+      else
+        @logger.debug("RC file not found. Not loading: #{rc_path}")
+      end
     end
   end
 end