what happened and when in a git repo

who_did_it.rb

#!/usr/bin/env ruby
git_dir=ARGV[0].nil? ? "." : ARGV[0]  
since=ARGV[1].nil? ? 7: ARGV[1]
git_log = ""
Dir.chdir(git_dir) do
  git_log = %x{git log --since="#{since} days ago"  --format=%an | sort | uniq -c}
end
git_data = git_log.split("\n")
total_authors = git_data.size
total_commits = 0
git_data.each do |data|
  commits, author = data.split("\s")
  total_commits += commits.strip.to_i
end
puts "In the last #{since} days #{total_authors} developers have made #{total_commits} commits to #{git_dir}"