commit-msg hook to add a prefix to commit messages

commit-msg

#!/usr/bin/env ruby

# Adapted from
# https://gist.github.com/EmmanuelOga/2926764

# Convert a message to include branch name information.
class Transmogrifier < Struct.new(:message, :branchname)
  NOREF_MATCHER  = /#noref/
  BRANCHES_TO_SKIP = ['master', 'develop', 'staging']
  PREFIX_MATCHER = /\A([a-zA-Z]+[-_]\d+)[-_]/
  PREFIX_FORMAT = "[%s] %s"

  def prefix
    (branchname.to_s[PREFIX_MATCHER, 1] || "").split(/[_-]/).join("-").upcase.strip
  end

  def to_s
    return message if BRANCHES_TO_SKIP.include? branchname
    return message unless prefix =~ /\S/

    if message =~ NOREF_MATCHER
      output = message.gsub(NOREF_MATCHER, "")

    elsif message.include?(prefix)
      output = message

    else
      output = PREFIX_FORMAT % [prefix, message]
    end

    output.squeeze(" ").strip
  end
end

# Overwrites the file which holds the commit message with a fancier one.
def run!
  branchname   = `git branch --no-color 2> /dev/null`[/^\* (.+)/, 1].to_s
  message_path = ARGV.first
  message      = File.read(message_path).strip.chomp

  File.open(message_path, 'w') {|f| f.write Transmogrifier.new(message, branchname) }
end

run!