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'
require 'rubocop'
require 'byebug'

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(' ')

any ? system("git ls-files --modified --others --exclude-standard") #get a list of all modified and new files that aren't staged

if any? system("git stash git stash -k -u") # stash all unstaged files
status = system("rubocop -a #{changed_files}") unless changed_files.empty?
if any? system("git stash pop") # pop the latest stashed files

exit status.to_s[-1].to_i