Simple per-branch databases in Rails dev. Also different adapters for JRuby vs. MRI.

database.yml

shared: &shared
  # Use different adapters with JRuby vs. MRI
  adapter: <%= defined?(JRuby) ? "jdbcmysql" : "mysql" %>
  encoding: utf8
  username: root
  password:
  host: localhost
  socket: /opt/local/var/run/mysql5/mysqld.sock

<%
  # For the git branches listed in DB_BRANCHES, use a dev DB with the same name.
  # For other branches, use the DEFAULT_DB.
  DEFAULT_DB  = 'myproject_dev'
  DB_BRANCHES = %w[ t123 t456 ]
  branch = `git symbolic-ref HEAD 2> /dev/null`.chomp.split('/').last
  dev_db = DB_BRANCHES.include?(branch) ? branch : DEFAULT_DB
  puts "Using dev database: #{dev_db.inspect}"
%>
development:
  <<: *shared
  database: <%= dev_db %>