use your git branch and some regex rules to determine which db to use

branch_databases.yml

# This file reads in the current git branch and bases your database name on the rules you setup here
# if no output is given, use the capture from the select.
# if output given, lambda may access the matcher regex object, or just return a string

# match multiple branches, all share a db.
shared_db_for_all_cats:
  select: ^(cat)

# match multiple, individual db
db_for_each_cat:
  select: (feature_\w?)

# match multiple branches, each has individual db

db_for_each_feature:
  select: /^test_feature_\w?/
  output: lambda { |matcher| matcher.to_s }

# match multiple branches, all share a db.
shared_db_for_branches:
  select: /_similar_branch/
  output: lambda { "shared_branch_name" }

database.yml

defaults: &defaults

  adapter:  mysql

  username: abcd

  password: abcd
  host:     localhost



<%

  branch_file = "#{RAILS_ROOT}/config/branch_databases.yml"

  branches = File.file?(branch_file) ? YAML.load_file(branch_file) : {}



  git_branches = `cd "#{RAILS_ROOT}"; git branch --no-color`

  output = ''

  if $?.to_i == 0

    current_branch = git_branches.split("\n").detect { |b| b.match(/\A\*/) }.gsub(/\A\* /, '')

    match = branches.detect{|name,branch| current_branch.match branch['select'] }

    if match

      if match[1]['output']

        output = "_#{eval(match[1]['output']).call(current_branch)}"

      else

        output = "_#{$&}" 

      end

    end

  end



  puts "-- Branch database in use: #{output}" unless output.blank?

%>



development:

  database: myapp_development<%= output %>

  <<: *defaults

  

production:

  database: myapp_<%= output %>

  <<: *defaults



test: &test
  database: myapp_test<%= output %>

  <<: *defaults


cucumber:
  <<: *test