Rubocop Pre-Commit Hook

pre-commit

#!/usr/bin/env ruby
# Put this file in .git/hooks/pre-commit

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(' ')

system("bundle exec rubocop #{changed_files} -a") unless changed_files.empty?

exit $CHILD_STATUS.to_s[-1].to_i