gitstats.rb

def extract_log(dir)
  `(cd #{dir} && git log --oneline --shortstat --pretty=format:%aE)`
end

def extract_stats(log_string)
  log_string.split(/\n\n/).map do |log_entry|
    StatEntry.new log_entry
  end
end

def log(msg)
  $stderr.puts msg
end

class StatEntry
  def initialize(log_entry)
    self.author, self.stats = log_entry.split(/\n/)
  end

  def changes
    splitted_numbers[0] || 0
  end

  def insertions
    splitted_numbers[1] || 0
  end

  def deletions
    splitted_numbers[2] || 0
  end

  def to_hash
    {}
  end

  def inspect
    "#<StatEntry #{author}: c#{changes} +#{insertions} -#{deletions}>"
  end

  public

  attr_reader :author

  protected

  attr_writer :author
  attr_accessor :stats

  private

  def splitted_numbers
    @_stats ||= (stats || "").scan(/\d+/).map(&:to_i)
  end
end

class AccumulatedEntry
  def initialize(author)
    self.author = author
    self.commits = 0
    self.changes = 0
    self.insertions = 0
    self.deletions = 0
  end

  def accumulate(stat_entry)
    self.commits += 1
    self.changes += stat_entry.changes
    self.insertions += stat_entry.insertions
    self.deletions += stat_entry.deletions
  end

  attr_reader :author, :commits, :changes, :insertions, :deletions

  protected

  attr_writer :author, :commits, :changes, :insertions, :deletions
end

statistics = Hash.new do |stats, author|
  stats[author] = AccumulatedEntry.new(author)
end

total_count = ARGV.size
log "Running over #{total_count} repos"

ARGV.each.with_index do |bare_repo, i|
  log "  *  #{bare_repo} (#{i+1}/#{total_count})"
  stat_entries = extract_stats(extract_log(bare_repo))

  stat_entries.each do |stat_entry|
    statistics[stat_entry.author].accumulate stat_entry
  end
end

puts 'author,commits,changes,insertions,deletions'
statistics.values.each do |accumulated_entry|
  puts [
        accumulated_entry.author,
        accumulated_entry.commits,
        accumulated_entry.changes,
        accumulated_entry.insertions,
        accumulated_entry.deletions
       ].join(',')
end