post-checkout for changing database name in rails projects. place this file into .git/hooks folder.

post-checkout

#!/usr/bin/ruby

require 'yaml'

class Database
  attr_reader :config_file, :settings

  def initialize
    @config_file = File.expand_path(File.join(File.dirname(__FILE__), "../../config/database.yml"))

    load_config
  end

  def change_branch_database!
    settings.each do |key, value|
      value["database"] = prepare_database_name(value['database'])
    end

    save_settings
  end

  private

  def prepare_database_name(name)
    name.gsub!(/#{delimeter}.+/,'')

    return "#{name}#{delimeter}#{branch_name}" unless branch_master?

    name
  end

  def save_settings
    File.open(config_file, "w") do |file|
      file.write(settings.to_yaml)
    end
  end

  def branch_master?
    branch_name == "master"
  end

  def branch_name
    @branch_name ||= `git branch --contains #{ARGV[1]}`.gsub('* ', '').strip
    @branch_name
  end

  def delimeter
    "---"
  end

  def load_config
    @settings = YAML.load(File.open(config_file, "r"))
  end
end

database = Database.new
database.change_branch_database!