Use rubocop to enforce a few styling rules

.rubocop.yml

@@ -0,0 +1,32 @@
+AllCops:
+  TargetRubyVersion: 3.0
+  DisabledByDefault: true
+  SuggestExtensions: false
+
+Layout/TrailingWhitespace:
+  Enabled: true
+
+Layout/TrailingEmptyLines:
+  Enabled: true
+
+Layout/IndentationConsistency:
+  Enabled: true
+
+Layout/CaseIndentation:
+  Enabled: true
+  EnforcedStyle: end
+
+Layout/CommentIndentation:
+  Enabled: true
+
+Layout/IndentationStyle:
+  Enabled: true
+
+Layout/SpaceAroundKeyword:
+  Enabled: true
+
+Layout/SpaceBeforeComma:
+  Enabled: true
+
+Layout/SpaceAfterComma:
+  Enabled: true

Gemfile

@@ -17,6 +17,8 @@ gem "rake"
 gem "test-unit"
 gem "test-unit-ruby-core"
 
+gem "rubocop"
+
 gem "debug", github: "ruby/debug", platforms: [:mri, :mswin]
 
 if RUBY_VERSION >= "3.0.0" && !is_truffleruby

lib/irb/inspector.rb

@@ -46,7 +46,7 @@ class Inspector
     # Determines the inspector to use where +inspector+ is one of the keys passed
     # during inspector definition.
     def self.keys_with_inspector(inspector)
-      INSPECTORS.select{|k,v| v == inspector}.collect{|k, v| k}
+      INSPECTORS.select{|k, v| v == inspector}.collect{|k, v| k}
     end
 
     # Example

lib/irb/locale.rb

@@ -94,7 +94,7 @@ def load(file)
       end
     end
 
-    def find(file , paths = $:)
+    def find(file, paths = $:)
       dir = File.dirname(file)
       dir = "" if dir == "."
       base = File.basename(file)

test/irb/test_input_method.rb

@@ -170,4 +170,3 @@ def has_rdoc_content?
     end
   end
 end
-

test/irb/test_workspace.rb

@@ -91,7 +91,7 @@ def test_toplevel_binding_local_variables
         irb_path = "#{top_srcdir}/#{dir}/irb"
         File.exist?(irb_path)
       end or omit 'irb command not found'
-      assert_in_out_err(bundle_exec + ['-W0', "-C#{top_srcdir}", '-e', <<~RUBY , '--', '-f', '--'], 'binding.local_variables', /\[:_\]/, [], bug17623)
+      assert_in_out_err(bundle_exec + ['-W0', "-C#{top_srcdir}", '-e', <<~RUBY, '--', '-f', '--'], 'binding.local_variables', /\[:_\]/, [], bug17623)
         version = 'xyz' # typical rubygems loading file
         load('#{irb_path}')
       RUBY