show legacy branches in a git repo

legacy_branches.rb

require 'time'

DAY = 60 * 60 * 24

def print_branches(branches)
  by_author = Hash.new { |hash,key| hash[key] = {} }

  branches.each do |branch|
    lines = `git show -s --pretty=medium #{branch}`.lines
    # commit d8f1e9d4c755d46192db635e964a9b04d6882f90
    # (Merge: ...)
    # Author: Some Author <some_author@example.com>
    # Date:   Tue Aug 19 11:29:28 2014 +0800
    #
    #    Some kind of message goes here
  
    commit = lines.shift.gsub(/commit\s/, '').strip
    author = lines.shift
    author = lines.shift if author[/Merge/] # Merge commit has an extra line
    author = author.gsub(/Author:\s+/, '').strip
    date = Time.parse(lines.shift.gsub(/Date:\s+/, '').strip)

    if (Time.now - date) / DAY > 30
      by_author[author][branch] = { commit: commit, date: date, message: lines.join('') }
    end
  end

  authors = by_author.keys.sort do |a, b|
    by_author[b].length - by_author[a].length
  end

  authors.each do |author|
    puts "(#{by_author[author].length}) #{author}"

    branches = by_author[author].keys.sort do |a,b|
      by_author[author][a][:date] - by_author[author][b][:date]
    end

    branches.each do |branch|
      puts "\t#{branch}"
      branch = by_author[author][branch]
      puts "\t\t #{((Time.now - branch[:date]) / (60 * 60 * 24)).to_i} days old"
      puts "\t\t #{branch[:commit]}"
    end
    puts "\n"
  end
end



puts "Merged branches"
puts "==============="

print_branches(`git branch -r --merged`.lines.map(&:strip))

puts "Unmerged branches"
puts "================="

print_branches(`git branch -r --no-merged`.lines.map(&:strip))