list remote branches sorted by age

branch_ages.rb

require 'date'

branch_times = `git remote show origin`.split("\n").grep(/tracked/).map do |line|
  name = line.split(' ').first
  last_log = `git log -n1 origin/#{name}`
  last_time = Date.parse(last_log.split("\n").grep(/^Date/).first.sub(/^Date\s+/, ''))
  [name, last_time.to_date]
end.sort_by(&:last)

branch_name_maxlen = branch_times.map(&:first).map(&:size).max
branch_times.each do |name, date|
  puts "%-#{branch_name_maxlen}s #{date}" % name
end