rubocop.rb

#!/usr/bin/env ruby

changed = `git diff --numstat origin/master | awk '{ print $3 }' | grep -E '(\\.rb|\\.rake)$' | grep -v db/schema`

changed = changed.split("\n").select { |c| File.exist?(c) }

if changed.length > 0
  system "bundle exec rubocop #{ARGV.join(' ')} #{changed.join(' ')}"
else
  puts "No changes."
end

teg_rubocop.yml

AllCops:
  Exclude:
    - 'features/**'
    - 'db/**'
  RunRailsCops: true

AlignHash:
  EnforcedLastArgumentHashStyle: always_ignore

AlignParameters:
  Enabled: false

LineLength:
  Max: 180

ClassLength:
  Enabled: true
  Severity: refactor
  Max: 300

MethodLength:
  Enabled: true
  Max: 30
  Severity: refactor

CyclomaticComplexity:
  Max: 10
  Severity: refactor

EndAlignment:
  Enabled: false

StringLiterals:
  Enabled: false

Documentation:
  Enabled: false

PercentLiteralDelimiters:
  PreferredDelimiters:
    '%w': '{}'

MethodDefParentheses:
  Enabled: false

PredicateName:
  NamePrefixBlacklist:
    - is_
    - have_

IndentHash:
  EnforcedStyle: consistent

# breaks using if blocks with assignments
IndentationWidth:
  Enabled: false

CaseIndentation:
  IndentWhenRelativeTo: end

FormatString:
  Enabled: false

ActionFilter:
  Enabled: false

# different methods calls that do exactly the same thing are a smell, regardless of semantics
SignalException:
  EnforcedStyle: only_raise

# Files in lib/migrations are allowed to puts things
Rails/Output:
  Exclude:
    - lib/migrations/*
    - script/*

Rails/DefaultScope:
  Include:
    - app/models/*.rb
    - app/models/**/*.rb

Rails/HasAndBelongsToMany:
  Enabled: false

Rails/ScopeArgs:
  Include:
    - app/models/*.rb
    - app/models/**/*.rb

Rails/Validation:
  Include:
    - app/models/*.rb
    - app/models/**/*.rb