fix: use ">= <current autoproj version>" as constraint in the default…

… gemfile

It ensures that the Gemfile uses "the autoproj that was used during
install or later", reducing the possibility of triggering a behavior
in Bundler such as rubygems/rubygems#6226

Rakefile

@@ -20,6 +20,7 @@ task "bootstrap" do
     %w[bootstrap install].each do |install_script|
         bootstrap_code = File.read(File.join(Dir.pwd, "bin", "autoproj_#{install_script}.in"))
                              .gsub("require 'autoproj/ops/install'", autoproj_ops_install)
+                             .gsub('#{Autoproj::VERSION}', Autoproj::VERSION) # rubocop:disable Lint/InterpolationCheck
         File.open(File.join(Dir.pwd, "bin", "autoproj_#{install_script}"), "w") do |io|
             io.write bootstrap_code
         end

bin/autoproj_bootstrap

@@ -269,7 +269,7 @@ module Autoproj
             # @param [String] autoproj_version a constraint on the autoproj version
             #   that should be used
             # @return [String]
-            def default_gemfile_contents(autoproj_version = ">= 2.0.0")
+            def default_gemfile_contents(autoproj_version = ">= 2.16.0")
                 ["source \"#{gem_source}\"",
                  "ruby \"#{RUBY_VERSION}\" if respond_to?(:ruby)",
                  "gem \"autoproj\", \"#{autoproj_version}\""].join("\n")

bin/autoproj_install

@@ -269,7 +269,7 @@ module Autoproj
             # @param [String] autoproj_version a constraint on the autoproj version
             #   that should be used
             # @return [String]
-            def default_gemfile_contents(autoproj_version = ">= 2.0.0")
+            def default_gemfile_contents(autoproj_version = ">= 2.16.0")
                 ["source \"#{gem_source}\"",
                  "ruby \"#{RUBY_VERSION}\" if respond_to?(:ruby)",
                  "gem \"autoproj\", \"#{autoproj_version}\""].join("\n")

lib/autoproj/ops/install.rb

@@ -259,11 +259,10 @@ def self.guess_gem_program
             # @param [String] autoproj_version a constraint on the autoproj version
             #   that should be used
             # @return [String]
-            def default_gemfile_contents(autoproj_version = ">= 2.0.0")
+            def default_gemfile_contents(autoproj_version = ">= #{Autoproj::VERSION}")
                 ["source \"#{gem_source}\"",
                  "ruby \"#{RUBY_VERSION}\" if respond_to?(:ruby)",
-                 "gem \"autoproj\", \"#{autoproj_version}\"",
-                 "gem \"utilrb\", \">= 3.0.1\""].join("\n")
+                 "gem \"autoproj\", \"#{autoproj_version}\""].join("\n")
             end
 
             def add_seed_config(path)