A script that prepends elm or ex depending on what gets commited

prepare-commit-msg

#!/usr/bin/env ruby

require 'set'

message = ARGV[0] # the file that contains the message (change this!)
source = ARGV[1] # can be template, merge, squash, commit 
commit_id = ARGV[2]

if ["merge","squash"].include?(source)
  return 1 # do nothing
end

files = `git diff --cached --name-only`.split("\n")


config = {
  "assets/elm" => "elm",
  "lib" => "ex"
}

tags = Set.new

files.each do |f|
  config.each do |pattern, prefix|
    if f.match?(pattern)
      tags.add(prefix)
    end
  end
end



if tags.to_a.any?
  old_lines = ["[#{tags.to_a.join(",")}] "] + File.readlines(message)
  File.open(message, 'w') do |fo|
    old_lines.each do |line|
      fo.puts  line
    end
  end
end