Rubocop pre-commit hook

gistfile1.rb

#!/usr/bin/env ruby
# This is a modified version of https://gist.github.com/mpeteuil/6147292

require 'english'
require 'rubocop'

ADDED_OR_MODIFIED = /A|AM|^M/.freeze

changed_files = `git status --porcelain`.split(/\n/).
    select { |file_name_with_status|
      file_name_with_status =~ ADDED_OR_MODIFIED
    }.
    map { |file_name_with_status|
      file_name_with_status.split(' ')[1]
    }.
    select { |file_name|
      File.extname(file_name) == '.rb'
    }.join(' ')

unless changed_files.empty?
  puts "\n\n FIXING STYLEGUIDES WITH RUBOCOP \n\n"
  rubocop = system("rubocop -a --force-exclusion #{changed_files}")

  if rubocop
    system("git add #{changed_files}")
  else
    puts "\n\n\e[31mPlease fix the affected files, rubocop was not able to fix them.\e[0m\n\n"
    exit 1
  end
end

exit $CHILD_STATUS.to_s[-1].to_i