Find the difference between a file and X changes ago

gistfile1.txt

#!/usr/bin/ruby
# Finds the difference between a file and X changes ago
# gitdifflast path/to/file 2
# would be the difference between this version and two changes ago (when the file actually changed not just commits)
# this distinguishes between the last change and the last commit
# use "git diff HEAD@{1} path/to/file" or "git diff HEAD^ path/to/file" for that

file = ARGV.shift
change_increment = ARGV.shift.to_i

log_output = `git log --oneline #{file}`
diff_change_line = log_output.to_a[change_increment]
refspec = diff_change_line.split(" ").first

diff_output = `git diff #{refspec} #{file}`

puts diff_output