Find top committers for a file in a git repo

top_committers.rb

#!/usr/bin/env ruby

require "json"
require "fileutils"

file = ARGV[0]

repo = `git rev-parse --show-toplevel`.strip
path = Dir.pwd.gsub(repo, File.basename(repo))
cache = Dir.home + "/.cache/top_committers/#{path}/#{file}"

FileUtils.mkdir_p(File.dirname(cache))

if File.exist?(cache)
  json = JSON.load_file(cache)
  sha = json["last_commit"]
  commits = json["commits"].map { |h| h.transform_keys(&:to_sym) }

  str = `git log --pretty="format:%an" --numstat #{sha}..HEAD -- #{file}`
else
  commits = []
  str = `git log --pretty="format:%an" --numstat -- #{file}`
end

commits += str.split("\n\n").map do |l|
  data = l.split(/\t|\n/)[0..2]

  {
    author: data[0],
    added: data[1],
    deleted: data[2],
  }
end

File.write(cache, JSON.dump({last_commit: `git rev-parse HEAD`[0..6], commits: commits}))

totals = commits.group_by { |c| c[:author] }.transform_values do |arr|
  arr.sum { |c| c[:added].to_i + c[:deleted].to_i }
end

puts "#{file} by author:"
puts totals.sort_by { |_,v| -v }.map { |k,v| "#{k}: #{v}" }