git_time_calcultor.rb

#! /usr/bin/env ruby
# encoding: UTF-8

require 'date'

since = ARGV.shift || Date.today

logs = `git log --since="#{since}" --pretty=format:"%H,%ae,%ai"`
all_commits = logs.split("\n").map{|i| i.split(",") }

if all_commits.empty?
  puts "No commits found since #{since}"
  exit
end

def parse_time(time)
  DateTime.parse(time).to_time
end

def get_hours(commits)
  t1 = parse_time(commits.first[2])
  t2 = parse_time(commits.last[2])
  ((t1 - t2) / 3600).round(3)
end

def stats_for(label, commits)
  indent = " " * (20 - label.length).abs
  hours = get_hours(commits)
  print "#{indent}#{label}:\t"
  print hours
  print " hours"
  puts
end

stats_for("Total", all_commits)

all_commits.group_by{|i| i[1] }.each do |user, user_commits|
  stats_for(user, user_commits)
end