git pre-commit hook to check for problem files before commiting

pre-commit.rb

#!/usr/bin/env ruby

problems = []

checks = {
            #'_spec\.rb$' => ['focus:[:space:]*true'],
            '\.rb$' => [
                        'binding.pry',
                        'debugger',
                        'if true',
                        'if false'
                       ]
         }

# Get names of all files that have been (A)dded, (C)opied, or (M)odified
# and that are staged to be part of the next commit
filenames = `git diff --cached --name-only --diff-filter=ACM`.split("\n")

filenames.each do |filename|
  checks.each do |filename_pattern, patterns|
    if filename.match filename_pattern
      patterns.each do |contents_pattern|
        new_lines_of_code = `git diff --cached #{filename} | ag -Q "\+" | ag "#{contents_pattern}"`
        results = new_lines_of_code.split("\n").map { |r| r.sub(/^\+[\s\t]*/, '') }
        if $? == 0
          # Add the relevant change with line number to the problems array
          results.each{ |r|
            problems.push "#{filename}:" + `ag -n '#{r}' #{filename}`.sub(/:\s+/, ' ').chomp
          }
        end
      end
    end
  end
end

if problems.any?
  puts "\e[33m>>> Please remove the following problems from these files before committing\e[0m"
  puts problems.join("\n")
else
end

exit 1 if problems.any?