parse_codeowners.rb

# Usage
# 1) Switch to the branch you want to look at locally
# 2) Make sure you have the version of wip that you want to compare against. You may need to fetch first.
# 3) Run the script

GREEN = 32
YELLOW = 33
BLUE = 34
class Match
  attr_reader :owner, :changed_line, :best_match
  def initialize(owner:, changed_line:, best_match:)
    @owner = owner
    @changed_line = changed_line
    @best_match = best_match
  end
end

def find_best_match(potential_matches, prospect)
  if match = potential_matches[prospect]
    [match, prospect]
  else
    parts = prospect.split("/")
    if parts.length == 1 # can't recurse any further
      return [nil, nil]
    end
    find_best_match(potential_matches, parts[0...-1].join("/"))
  end
end

def gen_ownership
  ownership = File.read('CODEOWNERS').split("\n").reduce({}) do |ownership, line|
    file, owner = line.split(" ")
    if file.nil? || owner.nil? || file.start_with?("#") # ignore non-parseable lines and comments
      next ownership
    end
    file = file[0...-1] if file.end_with?("/") # the codeowners file ends directories with '/'
    file = file[1..-1] if file.start_with?("/") # the codeowners file starts directories with '/'
    ownership[file] = owner
    ownership
  end
end

def gen_changed
  `git --no-pager diff wip --name-only`.split("\n")
end

def colorize(str, color_code)
  "\e[#{color_code}m#{str}\e[0m"
end

ownership = gen_ownership
matches = []
gen_changed.reduce(matches) do |acc, line|
  owner, best_match = find_best_match(ownership, line)
  next matches unless owner # exclude files w/o matches
  match = Match.new(owner: owner, changed_line: line, best_match: best_match)
  acc << match
  acc
end
matches.each do |match|
  puts "#{colorize(match.owner, GREEN)} owns #{colorize(match.changed_line, YELLOW)} because of match #{colorize(match.best_match, BLUE)}"
end