Rubocop precommit git hook for ruby apps that need cleanup as new features are coming along

pre-commit-rubocop

# Place in your project here: .git/hooks/pre-commit

# Runs all cops on newly added files
# Runs standard cops on files that have been modified

#!/usr/bin/env ruby

require 'rubocop'

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

ADDED = /A/.freeze
MODIFIED = /AM|^M/.freeze

changed_files = get_files(MODIFIED)
added_files = get_files(ADDED)

system("rubocop #{changed_files}") unless changed_files.empty?
system("rubocop -c .rubocop_full.yml #{added_files}") unless added_files.empty?

exit $CHILD_STATUS.to_s[-1].to_i