http://jsfiddle.net/NFzyR/1/

git_fs_activity_hash.rb

#require 'awesome_print'
require 'json'

module OMGWidgets ; end
module OMGWidgets::ActivityPartition
  class DirCounter
    attr_accessor :parent, :name, :hits, :children, :files

    def initialize(parent=nil)
      @hits = 0
      @parent = parent

      @children = Hash.new do |h, k|
        h[k] = DirCounter.new self
      end
    end

    def hit(*segments)
      next_seg = segments.shift
      @name ||= next_seg

      if segments.length < 2
        @hits += 1
      else
        # chain it down
        children[next_seg].hit *segments
      end
    end

    def to_hash
      hash = {
        :name => @name
      }

      hash[:hits] = @hits if @hits > 0

      hash[:children] = [] unless @children.empty?

      @children.each do |cname, counter|
        hash[:children] << counter.to_hash
      end

      hash
    end
  end


  repo_path = ARGV[0] || Dir.pwd
  limit = ARGV[1] || '--since="3 week ago"'
  commits = %x[cd #{repo_path} && git log --all --no-merges --pretty="%H" #{limit}].split("\n")


  root_dir = DirCounter.new
  root_dir.name = :/

  commits.each do |commit|
    files = %x[cd #{repo_path} && git show --pretty="format:" --name-only #{commit}].split("\n")

    files.each do |file|
      segments = file.split(File::SEPARATOR)
      root_dir.hit *segments
    end
  end

  puts JSON.dump root_dir.to_hash
end