Maintenance: Updated bin/bundle script to the new bundler default (rails removed the script from the default template).

bin/bundle

@@ -1,5 +1,122 @@
 #!/usr/bin/env ruby
 # Copyright (C) 2012-2021 Zammad Foundation, http://zammad-foundation.org/
 
-ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../Gemfile', __dir__)
-load Gem.bin_path('bundler', 'bundle')
+# frozen_string_literal: true
+
+#
+# This file was generated by Bundler.
+#
+# The application 'bundle' is installed as part of a gem, and
+# this file is here to facilitate running it.
+#
+
+require 'rubygems'
+
+m = Module.new do
+  module_function
+
+  def invoked_as_script?
+    File.expand_path($PROGRAM_NAME) == File.expand_path(__FILE__)
+  end
+
+  def env_var_version
+    ENV['BUNDLER_VERSION']
+  end
+
+  def cli_arg_version # rubocop:disable Metrics/CyclomaticComplexity, Metrics/PerceivedComplexity
+    return if !invoked_as_script? # don't want to hijack other binstubs
+    return if !'update'.start_with?(ARGV.first || ' ') # must be running `bundle update`
+
+    bundler_version = nil
+    update_index = nil
+    ARGV.each_with_index do |a, i|
+      if update_index && update_index.succ == i && a =~ Gem::Version::ANCHORED_VERSION_PATTERN
+        bundler_version = a
+      end
+      next if a !~ %r{\A--bundler(?:[= ](#{Gem::Version::VERSION_PATTERN}))?\z}o
+
+      bundler_version = $1
+      update_index = i
+    end
+    bundler_version
+  end
+
+  def gemfile
+    gemfile = ENV['BUNDLE_GEMFILE']
+    return gemfile if gemfile && !gemfile.empty? # rubocop:disable Rails/Present
+
+    File.expand_path('../Gemfile', __dir__)
+  end
+
+  def lockfile
+    lockfile =
+      case File.basename(gemfile)
+      when 'gems.rb' then gemfile.sub(%r{\.rb$}, gemfile)
+      else "#{gemfile}.lock"
+      end
+    File.expand_path(lockfile)
+  end
+
+  def lockfile_version
+    return if !File.file?(lockfile)
+
+    lockfile_contents = File.read(lockfile)
+    return if lockfile_contents !~ %r{\n\nBUNDLED WITH\n\s{2,}(#{Gem::Version::VERSION_PATTERN})\n}o
+
+    Regexp.last_match(1)
+  end
+
+  def bundler_requirement
+    @bundler_requirement ||=
+      env_var_version || cli_arg_version ||
+      bundler_requirement_for(lockfile_version)
+  end
+
+  def bundler_requirement_for(version)
+    return "#{Gem::Requirement.default}.a" if !version
+
+    bundler_gem_version = Gem::Version.new(version)
+
+    requirement = bundler_gem_version.approximate_recommendation
+
+    return requirement if Gem::Version.new(Gem::VERSION) >= Gem::Version.new('2.7.0')
+
+    requirement += '.a' if bundler_gem_version.prerelease?
+
+    requirement
+  end
+
+  def load_bundler!
+    ENV['BUNDLE_GEMFILE'] ||= gemfile
+
+    activate_bundler
+  end
+
+  def activate_bundler
+    gem_error = activation_error_handling do
+      gem 'bundler', bundler_requirement
+    end
+    return if gem_error.nil?
+
+    require_error = activation_error_handling do
+      require 'bundler/version'
+    end
+    return if require_error.nil? && Gem::Requirement.new(bundler_requirement).satisfied_by?(Gem::Version.new(Bundler::VERSION))
+
+    warn "Activating bundler (#{bundler_requirement}) failed:\n#{gem_error.message}\n\nTo install the version of bundler this project requires, run `gem install bundler -v '#{bundler_requirement}'`"
+    exit 42
+  end
+
+  def activation_error_handling
+    yield
+    nil
+  rescue StandardError, LoadError => e
+    e
+  end
+end
+
+m.load_bundler!
+
+if m.invoked_as_script?
+  load Gem.bin_path('bundler', 'bundle')
+end