diff --git a/.travis.yml b/.travis.yml
index c6c42a08ba..1c005422c9 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,9 +2,9 @@ language: ruby
 cache:
   directories:
     - $HOME/.gem/ruby
+    - $HOME/Library/Caches/Homebrew/style
+    - $HOME/Library/Caches/Homebrew/tests
     - Library/Homebrew/vendor/bundle
-    # For parallel_rspec
-    - Library/Homebrew/tmp
 
 matrix:
   include:
diff --git a/Library/.rubocop.yml b/Library/.rubocop.yml
index 12886a5080..66e71027e2 100644
--- a/Library/.rubocop.yml
+++ b/Library/.rubocop.yml
@@ -23,23 +23,67 @@ FormulaAuditStrict/ComponentsRedundancy:
 FormulaAudit/Homepage:
   Enabled: true
 
-Metrics/AbcSize:
+# `system` is a special case and aligns on second argument
+Layout/AlignParameters:
   Enabled: false
 
+Layout/CaseIndentation:
+  EnforcedStyle: end
+
+Layout/EmptyLineBetweenDefs:
+  AllowAdjacentOneLineDefs: true
+
+Layout/IndentArray:
+  EnforcedStyle: special_inside_parentheses
+
+Layout/IndentHeredoc:
+  EnforcedStyle: unindent
+
+# conflicts with DSL-style path concatenation with `/`
+Layout/SpaceAroundOperators:
+  Enabled: false
+
+# favor parens-less DSL-style arguments
+Lint/AmbiguousOperator:
+  Enabled: false
+
+# so many of these in formulae and can't be autocorrected
+Lint/AmbiguousRegexpLiteral:
+  Enabled: false
+
+# favor parens-less DSL-style arguments
+Lint/AmbiguousBlockAssociation:
+  Enabled: false
+
+# assignment in conditions are useful sometimes
+Lint/AssignmentInCondition:
+  Enabled: false
+
+Lint/EndAlignment:
+  EnforcedStyleAlignWith: variable
+
+# so many of these in formulae and can't be autocorrected
+Lint/ParenthesesAsGroupedExpression:
+  Enabled: false
+
+# TODO: try to bring down all metrics maximums
+Metrics/AbcSize:
+  Max: 250
+
 Metrics/BlockLength:
-  Enabled: false
+  Max: 1250
 
 Metrics/ClassLength:
-  Enabled: false
+  Max: 1500
 
 Metrics/CyclomaticComplexity:
-  Enabled: false
+  Max: 75
 
 Metrics/LineLength:
-  Enabled: false
+  Max: 400
 
 Metrics/MethodLength:
-  Enabled: false
+  Max: 250
 
 Metrics/ModuleLength:
   CountComments: false
@@ -47,36 +91,19 @@ Metrics/ModuleLength:
     - '**/bin/**/*'
     - '**/cmd/**/*'
     - '**/lib/**/*'
-    - '**/spec/**/*'
 
 Metrics/PerceivedComplexity:
-  Enabled: false
+  Max: 80
 
-# favor parens-less DSL-style arguments
-Lint/AmbiguousOperator:
-  Enabled: false
-
-Lint/AmbiguousRegexpLiteral:
-  Enabled: false
-
-Lint/AssignmentInCondition:
-  Enabled: false
-
-Lint/EndAlignment:
-  EnforcedStyleAlignWith: variable
-
-Lint/ParenthesesAsGroupedExpression:
+# makes code less readable for minor performance increases
+Performance/Caller:
   Enabled: false
 
 Style/Alias:
   EnforcedStyle: prefer_alias
 
-Style/AlignHash:
-  Enabled: false
-
-# `system` is a special case and aligns on second argument
-Style/AlignParameters:
-  Enabled: false
+Style/AutoResourceCleanup:
+  Enabled: true
 
 Style/BarePercentLiterals:
   EnforcedStyle: percent_q
@@ -84,9 +111,6 @@ Style/BarePercentLiterals:
 Style/BlockDelimiters:
   EnforcedStyle: line_count_based
 
-Style/CaseIndentation:
-  EnforcedStyle: end
-
 Style/ClassAndModuleChildren:
   EnforcedStyle: nested
 
@@ -99,16 +123,22 @@ Style/CommandLiteral:
 Style/ConditionalAssignment:
   Enabled: false
 
+# most of our APIs are internal so don't require docs
 Style/Documentation:
  Enabled: false
 
-Style/EmptyLineBetweenDefs:
-  AllowAdjacentOneLineDefs: true
+Style/Encoding:
+  Enabled: true
 
 # dashes in filenames are typical
 Style/FileName:
   Regex: !ruby/regexp /^[\w\@\-\+\.]+(\.rb)?$/
 
+# falsely flags e.g. curl formatting arguments as format strings
+Style/FormatStringToken:
+  Enabled: false
+
+# so many of these in formulae and can't be autocorrected
 Style/GuardClause:
   Enabled: false
 
@@ -121,13 +151,6 @@ Style/HashSyntax:
     - '**/lib/**/*'
     - '**/spec/**/*'
 
-# disabled until it respects line length
-Style/IfUnlessModifier:
-  Enabled: false
-
-Style/IndentArray:
-  EnforcedStyle: special_inside_parentheses
-
 # only for numbers >= 1_000_000
 Style/NumericLiterals:
   MinDigits: 7
@@ -160,13 +183,6 @@ Style/RaiseArgs:
 Style/RegexpLiteral:
   EnforcedStyle: slashes
 
-# conflicts with DSL-style path concatenation with `/`
-Style/SpaceAroundOperators:
-  Enabled: false
-
-Style/SingleLineBlockParams:
-  Enabled: false
-
 # not a problem for typical shell users
 Style/SpecialGlobalVars:
   Enabled: false
@@ -179,17 +195,22 @@ Style/StringLiterals:
 Style/StringLiteralsInInterpolation:
   EnforcedStyle: double_quotes
 
+Style/SymbolArray:
+  EnforcedStyle: brackets
+
 Style/TernaryParentheses:
-  Enabled: false
+  EnforcedStyle: require_parentheses_when_complex
 
 # makes diffs nicer
 Style/TrailingCommaInLiteral:
   EnforcedStyleForMultiline: comma
+
 Style/TrailingCommaInArguments:
   EnforcedStyleForMultiline: comma
 
+# we have too many variables like sha256 where this harms readability
 Style/VariableNumber:
   Enabled: false
 
 Style/WordArray:
-  Enabled: false
+  MinSize: 4
diff --git a/Library/Homebrew/.rubocop.yml b/Library/Homebrew/.rubocop.yml
index 4158f9f644..26c9445294 100644
--- a/Library/Homebrew/.rubocop.yml
+++ b/Library/Homebrew/.rubocop.yml
@@ -9,9 +9,8 @@ AllCops:
     - '**/Casks/**/*'
     - '**/vendor/**/*'
 
-Style/BlockDelimiters:
+Layout/MultilineMethodCallIndentation:
   Exclude:
-    - '**/cask/spec/**/*'
     - '**/*_spec.rb'
 
 # so many of these in formulae but none in here
@@ -27,16 +26,13 @@ Lint/NestedMethodDefinition:
 Lint/ParenthesesAsGroupedExpression:
   Enabled: true
 
-Metrics/ModuleLength:
-  CountComments: false
-  Exclude:
-    - 'cask/lib/hbc/locations.rb'
-    - 'cask/lib/hbc/macos.rb'
-    - 'cask/lib/hbc/utils.rb'
-
 Metrics/ParameterLists:
   CountKeywordArgs: false
 
+Style/BlockDelimiters:
+  Exclude:
+    - '**/*_spec.rb'
+
 # so many of these in formulae but none in here
 Style/GuardClause:
   Enabled: true
diff --git a/Library/Homebrew/cask/lib/hbc/cli/style.rb b/Library/Homebrew/cask/lib/hbc/cli/style.rb
index 03159a0cf4..97208232b1 100644
--- a/Library/Homebrew/cask/lib/hbc/cli/style.rb
+++ b/Library/Homebrew/cask/lib/hbc/cli/style.rb
@@ -11,7 +11,8 @@ module Hbc
 
       def run
         install_rubocop
-        system({ "XDG_CACHE_HOME" => HOMEBREW_CACHE }, "rubocop", *rubocop_args, "--", *cask_paths)
+        cache_env = { "XDG_CACHE_HOME" => "#{HOMEBREW_CACHE}/style" }
+        system(cache_env, "rubocop", *rubocop_args, "--", *cask_paths)
         raise CaskError, "style check failed" unless $CHILD_STATUS.success?
         true
       end
diff --git a/Library/Homebrew/cmd/style.rb b/Library/Homebrew/cmd/style.rb
index 228aa360e2..e469c47bbb 100644
--- a/Library/Homebrew/cmd/style.rb
+++ b/Library/Homebrew/cmd/style.rb
@@ -73,7 +73,11 @@ module Homebrew
     args = %w[
       --force-exclusion
     ]
-    args << "--auto-correct" if fix
+    if fix
+      args << "--auto-correct"
+    else
+      args << "--parallel"
+    end
 
     if options[:except_cops]
       options[:except_cops].map! { |cop| RuboCop::Cop::Cop.registry.qualified_cop_name(cop.to_s, "") }
@@ -101,14 +105,16 @@ module Homebrew
       args += files
     end
 
+    cache_env = { "XDG_CACHE_HOME" => "#{HOMEBREW_CACHE}/style" }
+
     case output_type
     when :print
       args << "--display-cop-names" if ARGV.include? "--display-cop-names"
       args << "--format" << "simple" if files
-      system({ "XDG_CACHE_HOME" => HOMEBREW_CACHE }, "rubocop", *args)
+      system(cache_env, "rubocop", *args)
       !$?.success?
     when :json
-      json, _, status = Open3.capture3({ "XDG_CACHE_HOME" => HOMEBREW_CACHE }, "rubocop", "--format", "json", *args)
+      json, _, status = Open3.capture3(cache_env, "rubocop", "--format", "json", *args)
       # exit status of 1 just means violations were found; other numbers mean
       # execution errors.
       # exitstatus can also be nil if RuboCop process crashes, e.g. due to
diff --git a/Library/Homebrew/constants.rb b/Library/Homebrew/constants.rb
index 827d5827f2..4ccf186245 100644
--- a/Library/Homebrew/constants.rb
+++ b/Library/Homebrew/constants.rb
@@ -1,3 +1,3 @@
 # RuboCop version used for `brew style` and `brew cask style`
-HOMEBREW_RUBOCOP_VERSION = "0.47.1".freeze
-HOMEBREW_RUBOCOP_CASK_VERSION = "~> 0.12.0".freeze # has to be updated when RuboCop version changes
+HOMEBREW_RUBOCOP_VERSION = "0.49.1".freeze
+HOMEBREW_RUBOCOP_CASK_VERSION = "~> 0.13.0".freeze # has to be updated when RuboCop version changes
diff --git a/Library/Homebrew/dev-cmd/tests.rb b/Library/Homebrew/dev-cmd/tests.rb
index d903267684..f434868b61 100644
--- a/Library/Homebrew/dev-cmd/tests.rb
+++ b/Library/Homebrew/dev-cmd/tests.rb
@@ -91,12 +91,12 @@ module Homebrew
       end
 
       args = ["-I", HOMEBREW_LIBRARY_PATH/"test"]
-      args += %w[
+      args += %W[
         --color
         --require spec_helper
         --format progress
         --format ParallelTests::RSpec::RuntimeLogger
-        --out tmp/parallel_runtime_rspec.log
+        --out #{HOMEBREW_CACHE}/tests/parallel_runtime_rspec.log
       ]
 
       args << "--seed" << ARGV.next if ARGV.include? "--seed"
diff --git a/Library/Homebrew/extend/string.rb b/Library/Homebrew/extend/string.rb
index 162666d2dc..809242db91 100644
--- a/Library/Homebrew/extend/string.rb
+++ b/Library/Homebrew/extend/string.rb
@@ -2,6 +2,7 @@ class String
   def undent
     gsub(/^[ \t]{#{(slice(/^[ \t]+/) || '').length}}/, "")
   end
+  alias unindent undent
 
   # eg:
   #   if foo then <<-EOS.undent_________________________________________________________72
diff --git a/Library/Homebrew/test/Gemfile.lock b/Library/Homebrew/test/Gemfile.lock
index 1f6adae933..ccfd91542d 100644
--- a/Library/Homebrew/test/Gemfile.lock
+++ b/Library/Homebrew/test/Gemfile.lock
@@ -36,7 +36,8 @@ GEM
     rspec-support (3.6.0)
     rspec-wait (0.0.9)
       rspec (>= 3, < 4)
-    rubocop (0.48.1)
+    rubocop (0.49.1)
+      parallel (~> 1.10)
       parser (>= 2.3.3.1, < 3.0)
       powerpack (~> 0.1)
       rainbow (>= 1.99.1, < 3.0)