gistfile1.rb

#!/usr/bin/env ruby
#
# Example:
# $: git log --numstat -w --summary --date=iso | this.rb
# <timestamp> <added> <deleted>
#
require "time"

DATE = /^Date:(.*)/
DIFF = /^(\d+)\s+(\d+)/

def output(ts, add, del)
  return unless ts
  puts "#{ts}\t#{add}\t#{del}"
end

timestamp = nil
added = 0
deleted = 0

while line = STDIN.gets
  if line =~ DATE
    output(timestamp, added, deleted)
    timestamp = Time.parse($1).to_i
    added = 0
    deleted = 0
  elsif line =~ DIFF
    added += $1.to_i
    deleted += $2.to_i
  end
end  

output(timestamp, added, deleted)