From: Antonio Terceiro <terceiro@debian.org>
Date: Wed, 27 May 2015 09:36:17 -0300
Subject: Support system-installed plugins
Source: https://salsa.debian.org/ruby-team/vagrant/blob/cb672c6dc0c63f6552c5ec4d6d7d22929d353503/debian/patches/0004-Support-system-installed-plugins.patch

Plugins must be installed as regular Ruby libraries, and they must
contain /usr/share/vagrant-plugins/plugins.d/$PLUGINNAME.json with the
following content:

{
  "${PLUGINNAME}": {
    "ruby_version":"$(ruby -e 'puts RUBY_VERSION')",
    "vagrant_version":"$(cat /usr/share/vagrant/version.txt)",
    "gem_version":"",
    "require":"",
    "sources":[]
  }
}
---
 lib/vagrant/plugin/manager.rb    |  4 ++--
 lib/vagrant/plugin/state_file.rb | 22 +++++++++++++++++++++-
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/lib/vagrant/plugin/manager.rb b/lib/vagrant/plugin/manager.rb
index 567347d..d9d76a0 100644
--- a/lib/vagrant/plugin/manager.rb
+++ b/lib/vagrant/plugin/manager.rb
@@ -18,7 +18,7 @@ module Vagrant
 
       # Returns the path to the [StateFile] for system plugins.
       def self.system_plugins_file
-        dir = Vagrant.installer_embedded_dir
+        dir = '@system_plugin_dir@'
         return nil if !dir
         Pathname.new(dir).join("plugins.json")
       end
@@ -38,7 +38,7 @@ module Vagrant
 
         system_path  = self.class.system_plugins_file
         @system_file = nil
-        @system_file = StateFile.new(system_path) if system_path && system_path.file?
+        @system_file = StateFile.new(system_path, true) if system_path && system_path.file?
 
         @local_file = nil
         @globalized = @localized = false
diff --git a/lib/vagrant/plugin/state_file.rb b/lib/vagrant/plugin/state_file.rb
index c6872d4..935d431 100644
--- a/lib/vagrant/plugin/state_file.rb
+++ b/lib/vagrant/plugin/state_file.rb
@@ -11,8 +11,9 @@ module Vagrant
       # @return [Pathname] path to file
       attr_reader :path
 
-      def initialize(path)
+      def initialize(path, system = false)
         @path = path
+        @system = system
 
         @data = {}
         if @path.exist?
@@ -28,6 +29,21 @@ module Vagrant
 
         @data["version"] ||= "1"
         @data["installed"] ||= {}
+        load_extra_plugins
+      end
+
+      def load_extra_plugins
+        extra_plugins = Dir.glob(@path.dirname.join('plugins.d', '*.json'))
+        extra_plugins.each do |filename|
+          json = File.read(filename)
+          begin
+            plugin_data = JSON.parse(json)
+            @data["installed"].merge!(plugin_data)
+          rescue JSON::ParserError => e
+            raise Vagrant::Errors::PluginStateFileParseError,
+              path: filename, message: e.message
+          end
+        end
       end
 
       # Add a plugin that is installed to the state file.
@@ -107,6 +123,14 @@ module Vagrant
           f.close
           FileUtils.mv(f.path, @path)
         end
+      rescue Errno::EACCES
+        # Ignore permission denied against system-installed plugins; regular
+        # users are not supposed to write there.
+        raise unless @system
+      rescue Errno::EROFS
+        # Ignore read-only filesystem against system-installed plugins; regular
+        # users are not supposed to write there.
+        raise unless @system
       end
 
       protected