Print a histogram of merge commits by month for the current Git repository

merge-commits-by-date.rb

#!/usr/bin/env ruby

TEMPFILE = "/tmp/git-merge-dates.txt"

`git log --merges --pretty=format:"%ci" --date=short > #{TEMPFILE}`
puts "MONTH,COMMITS"
(2011..2016).each do |year|
  (1..12).each do |month|
    pattern = year.to_s + "-" + sprintf("%02d", month)
    result = `grep #{pattern} #{TEMPFILE} | wc -l`
    puts pattern + "," + result.strip
  end
end
`rm #{TEMPFILE}`