check-whitespace.rb

#!/usr/bin/ruby

diff = `git show`.lines.map { |l| l.sub("\n", '') }
file = nil
range = nil
removed = []
added = []

diff.each do |line|
    if line.start_with?('diff ')
        file = line.split[2]
        range = nil
        puts("\033[1;31mChanges in #{file}:\033[0m")
    elsif line.start_with?('@@ ')
        range = line.split[1..2] * ' '
        removed = []
        added = []
    elsif range
        if line.start_with?('-')
            removed << line
        elsif line.start_with?('+')
            added << line
        elsif line.start_with?(' ')
            if !removed.empty? && !added.empty?
                rem_str = removed.map { |l| l.sub(/^-/, '') } * "\n"
                add_str = added.map { |l| l.sub(/^\+/, '') } * "\n"

                add_str_collapsed = add_str.gsub(/\s+/, ' ')
                add_str_collapsed_expanded =
                    add_str_collapsed.gsub(/ ({\s*['"])(execute|return)/, "\n\\1\\2")

                if rem_str == add_str_collapsed_expanded
                    puts("(Whitespace expanded #{range})")
                else
                    puts("\033[1mChanged #{range}:\033[0m")
                    puts(removed * "\n")
                    puts(added * "\n")
                end
            elsif !removed.empty?
                puts("\033[1mRemoved #{range}:\033[0m")
                puts(removed * "\n")
            elsif !added.empty?
                puts("\033[1mAdded #{range}:\033[0m")
                puts(added * "\n")
            end

            removed = []
            added = []
        end
    end
end