Make use of Gemfile groups to avoid changes to Gemfile.lock after 'bundle install'.

Gemfile

@@ -11,8 +11,10 @@ gem 'activerecord-session_store'
 
 gem 'json'
 
-# Gems used only for assets and not required
-# in production environments by default.
+# Supported DBs
+gem 'mysql2', '~> 0.3.20', group: :mysql
+gem 'pg', group: :postgres
+
 group :assets do
   gem 'sass-rails' #, github: 'rails/sass-rails'
   gem 'coffee-rails'
@@ -57,33 +59,8 @@ gem 'libv8'
 gem 'execjs'
 gem 'therubyracer'
 
-# Include database gems for the adapters found in the database
-# configuration file, thanks to redmine, taken from https://github.com/redmine/redmine/blob/master/Gemfile
 require 'erb'
 require 'yaml'
-database_file = File.join(File.dirname(__FILE__), 'config/database.yml')
-if File.exist?(database_file)
-  database_config = YAML.load(ERB.new(IO.read(database_file)).result)
-  adapters = database_config.values.map { |c| c['adapter'] }.compact.uniq
-  if adapters.any?
-    adapters.each do |adapter|
-      case adapter
-      when 'mysql2'
-        gem 'mysql2', '~> 0.3.20'
-      when /postgresql/
-        gem 'pg'
-      when /sqlite3/
-        gem 'sqlite3'
-      else
-        warn("Unknown database adapter `#{adapter}` found in config/database.yml, use Gemfile.local to load your own database gems")
-      end
-    end
-  else
-    warn('No adapter found in config/database.yml, please configure it first')
-  end
-else
-  warn('Please configure your config/database.yml first')
-end
 
 gem 'net-ldap'
 
@@ -128,7 +105,6 @@ group :development, :test do
   gem 'pre-commit'
   gem 'rubocop'
   gem 'coffeelint'
-
 end
 
 gem 'puma'

README.md

@@ -27,8 +27,13 @@ Getting Started
 
 ```
      zammad@shell> cd zammad
-     zammad@shell> gem install rails
-     zammad@shell> bundle install
+     zammad@shell> gem install bundler
+
+     # For PostgreSQL (note, the option says "without ... mysql")
+     zammad@shell> bundle install --without test development mysql
+
+     # For MySQL (note, the option says "without ... postgres")
+     zammad@shell> bundle install --without test development postgres
 ```
 
 3. Configure your databases