use a database based on branch name then when you make a new branch rake db:{create,migrate,seed}

database.yml

database: &database
  adapter: # your database
  hostname: localhost
  username: root
  password:
  encoding: utf8

development:
  <<: *database
  <% branch_name = `git symbolic-ref HEAD`.strip.split('/')[-1] %>
  <% unless %w[master production staging].include?(branch_name) %>
  database: appname_<%= branch_name %>
  <% else %>
  database: appname_development
  <% end %>