Diff only current branch to master (even if master was updated after current branch creation)

diff-script.rb

#!/usr/bin/env ruby

# frozen_string_literal: true
require 'tempfile'

branch = ARGV.first || 'HEAD'

data = `git log --no-merges --author=login.hedin@gmail.com --oneline master..#{branch}`
commits = data.split("\n").map { |s| s.scan(/\w+ /).first.strip }
patch = ''
commits.each do |commit|
  commit_data = <<-SEPARATOR
----------------------------------------------------------------------
----------------------------------------------------------------------
------------------ PATCH FOR COMMIT: #{commit} -----------------------
----------------------------------------------------------------------
----------------------------------------------------------------------
SEPARATOR
  commit_data << `git show #{commit} --stat`
  commit_data << `git show #{commit} --unified=20`
  patch << commit_data
end

path = File.join Dir::Tmpname.tmpdir, Dir::Tmpname.make_tmpname('commits', '.diff')

File.open(path, 'w') { |f| f.write patch }
`atom -a #{path}`