Ruby style guide git pre-commit hook using Rubocop as the style guide checker. Only runs on staged ruby files that have been added and/or modified.

rubocop_pre_commit_hook

#!/usr/bin/env ruby
require 'english'

ADDED_OR_MODIFIED = /A|AM|^M/

added_or_modified = `git status --porcelain`.split("\n").select do |file_name_with_status|
  file_name_with_status =~ ADDED_OR_MODIFIED
end
filenames = added_or_modified.map do |file_name_with_status|
  file_name_with_status.split(' ')[1]
end
changed_ruby_files = filenames.select { |file| File.extname(file) == '.rb' }
exit if changed_ruby_files.empty?

puts 'Running Rubocop...'
system('rubocop', '-a', *changed_ruby_files)
rubocop_status = $CHILD_STATUS
system('git', 'add', *changed_ruby_files)

unless rubocop_status.success?
  puts "\nPlease fix rubocop errors before committing changes."
  exit rubocop_status.to_s[-1].to_i
end