#!/usr/bin/env ruby -w

treeish = ARGV.shift || 'HEAD'
output = nil
loop do
    puts "git diff-tree --color --cc #{treeish}"
    output = `git diff-tree --color --cc #{treeish}`
    len = output.strip.length == 40
    break if !$?.success? || len == 0 || len == 40
    treeish = `git log -n1 #{treeish} | head -n2 | tail -n1`.strip.split[1]
    puts treeish
    break unless treeish =~ /^[0-9a-f]{7}$/
end
puts output