11 files changed, 182 insertions, 1 deletions
diff --git a/lib/bundler/cli.rb b/lib/bundler/cli.rb
index 85851423..c3a9a01e 100644
--- a/lib/bundler/cli.rb
+++ b/lib/bundler/cli.rb
@@ -204,6 +204,8 @@ module Bundler
       "Force downloading every gem."
     method_option "ruby", :type => :boolean, :banner =>
       "Update ruby specified in Gemfile.lock"
+    method_option "bundler", :type => :string, :lazy_default => "> 0.a", :banner =>
+      "Update the locked version of bundler"
     def update(*gems)
       require "bundler/cli/update"
       Update.new(options, gems).run
diff --git a/lib/bundler/cli/update.rb b/lib/bundler/cli/update.rb
index 037da291..33b0557f 100644
--- a/lib/bundler/cli/update.rb
+++ b/lib/bundler/cli/update.rb
@@ -13,7 +13,7 @@ module Bundler
       sources = Array(options[:source])
       groups  = Array(options[:group]).map(&:to_sym)
 
-      if gems.empty? && sources.empty? && groups.empty? && !options[:ruby]
+      if gems.empty? && sources.empty? && groups.empty? && !options[:ruby] && !options[:bundler]
         # We're doing a full update
         Bundler.definition(true)
       else
diff --git a/lib/bundler/postit_trampoline.rb b/lib/bundler/postit_trampoline.rb
new file mode 100644
index 00000000..7406612e
--- /dev/null
+++ b/lib/bundler/postit_trampoline.rb
@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+postit_lib = File.expand_path("../vendor/postit/lib", __FILE__)
+$:.unshift(postit_lib)
+require "postit"
+require "rubygems"
+
+environment = BundlerVendoredPostIt::Environment.new([])
+version = Gem::Requirement.new(environment.bundler_version)
+
+installed_version =
+  if defined?(Bundler::VERSION)
+    Bundler::VERSION
+  else
+    File.read(File.expand_path("../version.rb", __FILE__)) =~ /VERSION = "(.+)"/
+    $1
+  end
+installed_version &&= Gem::Version.new(installed_version)
+
+if !version.satisfied_by?(installed_version)
+  begin
+    installer = BundlerVendoredPostIt::Installer.new(version)
+    installer.install!
+  rescue => e
+    abort <<-EOS.strip
+Installing the inferred bundler version (#{version}) failed.
+If you'd like to update to the current bundler version (#{installed_version}) in this project, run `bundle update --bundler`.
+The error was: #{e}
+    EOS
+  end
+
+  Gem.loaded_specs.delete("bundler") unless defined?(Bundler)
+  gem "bundler", version
+  $:.delete(File.expand_path("../..", __FILE__))
+else
+  begin
+    gem "bundler", version
+  rescue LoadError
+    $:.unshift(File.expand_path("../..", __FILE__))
+  end
+end
+
+running_version = begin
+  require "bundler/version"
+  Bundler::VERSION
+rescue LoadError, NameError
+  nil
+end
+
+if !Gem::Version.correct?(running_version.to_s) || !version.satisfied_by?(Gem::Version.create(running_version))
+  abort "The running bundler (#{running_version}) does not match the required `#{version}`"
+end
+
+$:.delete_at($:.find_index(postit_lib))
diff --git a/lib/bundler/setup.rb b/lib/bundler/setup.rb
index 9aae6478..c888dabf 100644
--- a/lib/bundler/setup.rb
+++ b/lib/bundler/setup.rb
@@ -1,4 +1,5 @@
 # frozen_string_literal: true
+require "bundler/postit_trampoline" unless ENV["BUNDLE_DISABLE_POSTIT"]
 require "bundler/shared_helpers"
 
 if Bundler::SharedHelpers.in_bundle?
diff --git a/lib/bundler/shared_helpers.rb b/lib/bundler/shared_helpers.rb
index e21d616e..01f1118d 100644
--- a/lib/bundler/shared_helpers.rb
+++ b/lib/bundler/shared_helpers.rb
@@ -169,6 +169,7 @@ module Bundler
 
       # Set BUNDLE_GEMFILE
       ENV["BUNDLE_GEMFILE"] = find_gemfile.to_s
+      ENV["BUNDLER_VERSION"] = Bundler::VERSION
     end
 
     def set_path
diff --git a/lib/bundler/vendor/postit/lib/postit.rb b/lib/bundler/vendor/postit/lib/postit.rb
new file mode 100644
index 00000000..4b3ff34d
--- /dev/null
+++ b/lib/bundler/vendor/postit/lib/postit.rb
@@ -0,0 +1,15 @@
+require 'postit/environment'
+require 'postit/installer'
+require 'postit/parser'
+require 'postit/version'
+require 'rubygems'
+
+module BundlerVendoredPostIt
+  def self.setup
+    load File.expand_path('../postit/setup.rb', __FILE__)
+  end
+
+  def self.bundler_version
+    defined?(Bundler::VERSION) && Bundler::VERSION
+  end
+end
diff --git a/lib/bundler/vendor/postit/lib/postit/environment.rb b/lib/bundler/vendor/postit/lib/postit/environment.rb
new file mode 100644
index 00000000..b758fa0c
--- /dev/null
+++ b/lib/bundler/vendor/postit/lib/postit/environment.rb
@@ -0,0 +1,44 @@
+require 'postit/parser'
+
+module BundlerVendoredPostIt
+  class Environment
+    def initialize(argv)
+      @argv = argv
+    end
+
+    def env_var_version
+      ENV['BUNDLER_VERSION']
+    end
+
+    def cli_arg_version
+      return unless str = @argv.first
+      str = str.dup.force_encoding('BINARY') if str.respond_to?(:force_encoding)
+      if Gem::Version.correct?(str)
+        @argv.shift
+        str
+      end
+    end
+
+    def gemfile
+      ENV['BUNDLE_GEMFILE'] || 'Gemfile'
+    end
+
+    def lockfile
+      File.expand_path case File.basename(gemfile)
+                       when 'gems.rb' then gemfile.sub(/\.rb$/, gemfile)
+                       else "#{gemfile}.lock"
+                       end
+    end
+
+    def lockfile_version
+      BundlerVendoredPostIt::Parser.new(lockfile).parse
+    end
+
+    def bundler_version
+      @bundler_version ||= begin
+        env_var_version || cli_arg_version ||
+          lockfile_version || "#{Gem::Requirement.default}.a"
+      end
+    end
+  end
+end
diff --git a/lib/bundler/vendor/postit/lib/postit/installer.rb b/lib/bundler/vendor/postit/lib/postit/installer.rb
new file mode 100644
index 00000000..4139038d
--- /dev/null
+++ b/lib/bundler/vendor/postit/lib/postit/installer.rb
@@ -0,0 +1,28 @@
+module BundlerVendoredPostIt
+  class Installer
+    def initialize(bundler_version)
+      @bundler_version = bundler_version
+    end
+
+    def installed?
+      if Gem::Specification.respond_to?(:find_by_name)
+        !Gem::Specification.find_by_name('bundler', @bundler_version).nil?
+      else
+        requirement = Gem::Requirement.new(@bundler_version)
+        Gem.source_index.gems.values.any? do |s|
+          s.name == 'bundler' && requirement.satisfied_by?(s.version)
+        end
+      end
+    rescue LoadError
+      false
+    end
+
+    def install!
+      return if installed?
+      require 'rubygems/dependency_installer'
+      installer = Gem::DependencyInstaller.new
+      installer.install('bundler', @bundler_version)
+      installer.installed_gems
+    end
+  end
+end
diff --git a/lib/bundler/vendor/postit/lib/postit/parser.rb b/lib/bundler/vendor/postit/lib/postit/parser.rb
new file mode 100644
index 00000000..98c4a357
--- /dev/null
+++ b/lib/bundler/vendor/postit/lib/postit/parser.rb
@@ -0,0 +1,21 @@
+require 'rubygems'
+
+module BundlerVendoredPostIt
+  class Parser
+    def initialize(file)
+      @file = file
+    end
+
+    BUNDLED_WITH =
+      /\n\nBUNDLED WITH\n\s{2,}(#{Gem::Version::VERSION_PATTERN})\n/
+
+    def parse
+      return unless lockfile = File.file?(@file) && File.read(@file)
+      if lockfile =~ BUNDLED_WITH
+        Regexp.last_match(1)
+      else
+        '< 1.10'
+      end
+    end
+  end
+end
diff --git a/lib/bundler/vendor/postit/lib/postit/setup.rb b/lib/bundler/vendor/postit/lib/postit/setup.rb
new file mode 100644
index 00000000..260edd55
--- /dev/null
+++ b/lib/bundler/vendor/postit/lib/postit/setup.rb
@@ -0,0 +1,12 @@
+require 'postit/environment'
+require 'postit/installer'
+
+environment = BundlerVendoredPostIt::Environment.new(ARGV)
+version = environment.bundler_version
+
+installer = BundlerVendoredPostIt::Installer.new(version)
+installer.install!
+
+gem 'bundler', version
+
+require 'bundler/version'
diff --git a/lib/bundler/vendor/postit/lib/postit/version.rb b/lib/bundler/vendor/postit/lib/postit/version.rb
new file mode 100644
index 00000000..1a165010
--- /dev/null
+++ b/lib/bundler/vendor/postit/lib/postit/version.rb
@@ -0,0 +1,3 @@
+module BundlerVendoredPostIt
+  VERSION = '0.1.2'.freeze
+end