Defaults to enabling rubocop cops

Explicitly pardons and builds a todo list of existing offences, with a view to correcting them over time.

.rubocop.yml

@@ -1,185 +1,16 @@
+inherit_from: .rubocop_todo.yml
+
 AllCops:
   TargetRubyVersion: 2.4
-  DisabledByDefault: true
-
-# Prefer &&/|| over and/or.
-Style/AndOr:
-  Enabled: true
-
-Layout/BlockAlignment:
-  Enabled: true
-
-# Do not use braces for hash literals when they are the last argument of a
-# method call.
-Style/BracesAroundHashParameters:
-  Enabled: true
-
-# Align `when` with `case`.
-Layout/CaseIndentation:
-  Enabled: true
-
-# Align comments with method definitions.
-Layout/CommentIndentation:
-  Enabled: true
-
-# No extra empty lines.
-Layout/EmptyLines:
-  Enabled: true
+  DisabledByDefault: false
 
 # Align `end` with the matching keyword or starting expression except for
 # assignments, where it should be aligned with the LHS.
 Layout/EndAlignment:
-  Enabled: true
   EnforcedStyleAlignWith: variable
 
-# Use Ruby >= 1.9 syntax for hashes. Prefer { a: :b } over { :a => :b }.
-Style/HashSyntax:
-  Enabled: true
-
-# Two spaces, no tabs (for indentation).
-Layout/IndentationWidth:
-  Enabled: true
-
-Layout/SpaceAfterColon:
-  Enabled: true
-
-Layout/SpaceAfterComma:
-  Enabled: true
-
-Layout/SpaceAfterNot:
-  Enabled: true
-
-Layout/SpaceAroundBlockParameters:
-  Enabled: true
-
-Layout/SpaceAroundEqualsInParameterDefault:
-  Enabled: true
-
-Layout/SpaceAroundKeyword:
-  Enabled: true
-
-Layout/SpaceAroundOperators:
-  Enabled: true
-
-Layout/SpaceBeforeComma:
-  Enabled: true
-
-Layout/SpaceBeforeFirstArg:
-    Enabled: true
-
-# Defining a method with parameters needs parentheses.
-Style/MethodDefParentheses:
-  Enabled: true
-
-# Use `foo {}` not `foo{}`.
-Layout/SpaceBeforeBlockBraces:
-  Enabled: true
-
-Layout/SpaceInsideArrayLiteralBrackets:
-  Enabled: true
-
-# Use `foo { bar }` not `foo {bar}`.
-Layout/SpaceInsideBlockBraces:
-  Enabled: true
-
-# Use `{ a: 1 }` not `{a:1}`.
-Layout/SpaceInsideHashLiteralBraces:
-  Enabled: true
-
-Layout/SpaceInsideParens:
-  Enabled: true
-
-# Detect hard tabs, no hard tabs.
-Layout/Tab:
-  Enabled: true
-
-# Blank lines should not have any spaces.
-Layout/TrailingBlankLines:
-  Enabled: true
-
-# No trailing whitespace.
-Layout/TrailingWhitespace:
-  Enabled: true
-
-# Use my_method(my_arg) not my_method( my_arg ) or my_method my_arg.
-Lint/RequireParentheses:
-  Enabled: true
-
 Layout/MultilineMethodCallIndentation:
-  Enabled: true
   EnforcedStyle: indented
 
-Layout/AlignHash:
-  Enabled: true
-
 Bundler/OrderedGems:
   Enabled: false
-
-Layout/ExtraSpacing:
-  Enabled: true
-
-Layout/LeadingCommentSpace:
-  Enabled: true
-
-Layout/EmptyLineAfterGuardClause:
-  Enabled: true
-
-Layout/EmptyLineAfterMagicComment:
-  Enabled: true
-
-Layout/EmptyLineBetweenDefs:
-  Enabled: true
-
-Layout/EmptyLinesAroundAccessModifier:
-  Enabled: true
-
-Layout/EmptyLinesAroundBlockBody:
-  Enabled: true
-
-Layout/EmptyLinesAroundClassBody:
-  Enabled: true
-
-Layout/EmptyLinesAroundExceptionHandlingKeywords:
-  Enabled: true
-
-Layout/EmptyLinesAroundMethodBody:
-  Enabled: true
-
-Layout/EmptyLinesAroundModuleBody:
-  Enabled: true
-
-Layout/AlignParameters:
-  Enabled: true
-
-Layout/ClosingParenthesisIndentation:
-  Enabled: true
-
-Layout/IndentHeredoc:
-  Enabled: true
-
-Layout/IndentationConsistency:
-  Enabled: true
-
-Layout/MultilineMethodCallBraceLayout:
-  Enabled: true
-
-Layout/MultilineOperationIndentation:
-  Enabled: true
-
-Lint/UselessAssignment:
-  Enabled: true
-
-Lint/UnusedMethodArgument:
-  Enabled: true
-
-Lint/UnusedBlockArgument:
-  Enabled: true
-
-Style/MethodCallWithoutArgsParentheses:
-  Enabled: true
-
-Lint/ParenthesesAsGroupedExpression:
-  Enabled: true
-
-Lint/DuplicateMethods:
-  Enabled: true