[ruby/irb] Page show_source's output

(https://github.com/ruby/irb/pull/719)

https://github.com/ruby/irb/commit/3cedc5cb62

lib/irb/cmd/show_source.rb

@@ -2,6 +2,7 @@
 
 require_relative "nop"
 require_relative "../source_finder"
+require_relative "../pager"
 require_relative "../color"
 
 module IRB
@@ -40,12 +41,16 @@ module IRB
       private
 
       def show_source(source)
-        puts
-        puts "#{bold("From")}: #{source.file}:#{source.first_line}"
-        puts
-        code = IRB::Color.colorize_code(File.read(source.file))
-        puts code.lines[(source.first_line - 1)...source.last_line].join
-        puts
+        file_content = IRB::Color.colorize_code(File.read(source.file))
+        code = file_content.lines[(source.first_line - 1)...source.last_line].join
+        content = <<~CONTENT
+
+          #{bold("From")}: #{source.file}:#{source.first_line}
+
+          #{code}
+        CONTENT
+
+        Pager.page_content(content)
       end
 
       def bold(str)

test/irb/test_irb.rb

@@ -6,6 +6,11 @@ require_relative "helper"
 module TestIRB
   class InputTest < IntegrationTestCase
     def test_symbol_aliases_are_handled_correctly
+      write_rc <<~RUBY
+        # disable pager
+        STDIN.singleton_class.define_method(:tty?) { false }
+      RUBY
+
       write_ruby <<~'RUBY'
         class Foo
         end
@@ -21,12 +26,11 @@ module TestIRB
     end
 
     def test_symbol_aliases_are_handled_correctly_with_singleline_mode
-      @irbrc = Tempfile.new('irbrc')
-      @irbrc.write <<~RUBY
+      write_rc <<~RUBY
+        # disable pager
+        STDIN.singleton_class.define_method(:tty?) { false }
         IRB.conf[:USE_SINGLELINE] = true
       RUBY
-      @irbrc.close
-      @envs['IRBRC'] = @irbrc.path
 
       write_ruby <<~'RUBY'
         class Foo
@@ -43,8 +47,6 @@ module TestIRB
       # Make sure it's tested in singleline mode
       assert_include output, "InputMethod: ReadlineInputMethod"
       assert_include output, "From: #{@ruby_file.path}:1"
-    ensure
-      @irbrc.unlink if @irbrc
     end
 
     def test_symbol_aliases_dont_affect_ruby_syntax